path: root/kernel/sched
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2013-01-22wake_up_process() should be never used to wakeup a TASK_STOPPED/TRACED taskOleg Nesterov
wake_up_process() should never wakeup a TASK_STOPPED/TRACED task. Change it to use TASK_NORMAL and add the WARN_ON(). TASK_ALL has no other users, probably can be killed. Signed-off-by: Oleg Nesterov <oleg@redhat.com> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-12-20sched: numa: ksm: fix oops in task_numa_placment()Hugh Dickins
task_numa_placement() oopsed on NULL p->mm when task_numa_fault() got called in the handling of break_ksm() for ksmd. That might be a peculiar case, which perhaps KSM could takes steps to avoid? but it's more robust if task_numa_placement() allows for such a possibility. Signed-off-by: Hugh Dickins <hughd@google.com> Acked-by: Mel Gorman <mgorman@suse.de> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-12-17Merge branch 'for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace Pull user namespace changes from Eric Biederman: "While small this set of changes is very significant with respect to containers in general and user namespaces in particular. The user space interface is now complete. This set of changes adds support for unprivileged users to create user namespaces and as a user namespace root to create other namespaces. The tyranny of supporting suid root preventing unprivileged users from using cool new kernel features is broken. This set of changes completes the work on setns, adding support for the pid, user, mount namespaces. This set of changes includes a bunch of basic pid namespace cleanups/simplifications. Of particular significance is the rework of the pid namespace cleanup so it no longer requires sending out tendrils into all kinds of unexpected cleanup paths for operation. At least one case of broken error handling is fixed by this cleanup. The files under /proc/<pid>/ns/ have been converted from regular files to magic symlinks which prevents incorrect caching by the VFS, ensuring the files always refer to the namespace the process is currently using and ensuring that the ptrace_mayaccess permission checks are always applied. The files under /proc/<pid>/ns/ have been given stable inode numbers so it is now possible to see if different processes share the same namespaces. Through the David Miller's net tree are changes to relax many of the permission checks in the networking stack to allowing the user namespace root to usefully use the networking stack. Similar changes for the mount namespace and the pid namespace are coming through my tree. Two small changes to add user namespace support were commited here adn in David Miller's -net tree so that I could complete the work on the /proc/<pid>/ns/ files in this tree. Work remains to make it safe to build user namespaces and 9p, afs, ceph, cifs, coda, gfs2, ncpfs, nfs, nfsd, ocfs2, and xfs so the Kconfig guard remains in place preventing that user namespaces from being built when any of those filesystems are enabled. Future design work remains to allow root users outside of the initial user namespace to mount more than just /proc and /sys." * 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace: (38 commits) proc: Usable inode numbers for the namespace file descriptors. proc: Fix the namespace inode permission checks. proc: Generalize proc inode allocation userns: Allow unprivilged mounts of proc and sysfs userns: For /proc/self/{uid,gid}_map derive the lower userns from the struct file procfs: Print task uids and gids in the userns that opened the proc file userns: Implement unshare of the user namespace userns: Implent proc namespace operations userns: Kill task_user_ns userns: Make create_new_namespaces take a user_ns parameter userns: Allow unprivileged use of setns. userns: Allow unprivileged users to create new namespaces userns: Allow setting a userns mapping to your current uid. userns: Allow chown and setgid preservation userns: Allow unprivileged users to create user namespaces. userns: Ignore suid and sgid on binaries if the uid or gid can not be mapped userns: fix return value on mntns_install() failure vfs: Allow unprivileged manipulation of the mount namespace. vfs: Only support slave subtrees across different user namespaces vfs: Add a user namespace reference from struct mnt_namespace ...
2012-12-17sched: numa: Fix build error if CONFIG_NUMA_BALANCING && ↵Mel Gorman
!CONFIG_TRANSPARENT_HUGEPAGE Michal Hocko reported that the following build error occurs if CONFIG_NUMA_BALANCING is set without THP support kernel/sched/fair.c: In function ‘task_numa_work’: kernel/sched/fair.c:932:55: error: call to ‘__build_bug_failed’ declared with attribute error: BUILD_BUG failed The problem is that HPAGE_PMD_SHIFT triggers a BUILD_BUG() on !CONFIG_TRANSPARENT_HUGEPAGE. This patch addresses the problem. Reported-by: Michal Hocko <mhocko@suse.cz> Signed-off-by: Mel Gorman <mgorman@suse.de> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-12-16Merge tag 'balancenuma-v11' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/mel/linux-balancenuma Pull Automatic NUMA Balancing bare-bones from Mel Gorman: "There are three implementations for NUMA balancing, this tree (balancenuma), numacore which has been developed in tip/master and autonuma which is in aa.git. In almost all respects balancenuma is the dumbest of the three because its main impact is on the VM side with no attempt to be smart about scheduling. In the interest of getting the ball rolling, it would be desirable to see this much merged for 3.8 with the view to building scheduler smarts on top and adapting the VM where required for 3.9. The most recent set of comparisons available from different people are mel: https://lkml.org/lkml/2012/12/9/108 mingo: https://lkml.org/lkml/2012/12/7/331 tglx: https://lkml.org/lkml/2012/12/10/437 srikar: https://lkml.org/lkml/2012/12/10/397 The results are a mixed bag. In my own tests, balancenuma does reasonably well. It's dumb as rocks and does not regress against mainline. On the other hand, Ingo's tests shows that balancenuma is incapable of converging for this workloads driven by perf which is bad but is potentially explained by the lack of scheduler smarts. Thomas' results show balancenuma improves on mainline but falls far short of numacore or autonuma. Srikar's results indicate we all suffer on a large machine with imbalanced node sizes. My own testing showed that recent numacore results have improved dramatically, particularly in the last week but not universally. We've butted heads heavily on system CPU usage and high levels of migration even when it shows that overall performance is better. There are also cases where it regresses. Of interest is that for specjbb in some configurations it will regress for lower numbers of warehouses and show gains for higher numbers which is not reported by the tool by default and sometimes missed in treports. Recently I reported for numacore that the JVM was crashing with NullPointerExceptions but currently it's unclear what the source of this problem is. Initially I thought it was in how numacore batch handles PTEs but I'm no longer think this is the case. It's possible numacore is just able to trigger it due to higher rates of migration. These reports were quite late in the cycle so I/we would like to start with this tree as it contains much of the code we can agree on and has not changed significantly over the last 2-3 weeks." * tag 'balancenuma-v11' of git://git.kernel.org/pub/scm/linux/kernel/git/mel/linux-balancenuma: (50 commits) mm/rmap, migration: Make rmap_walk_anon() and try_to_unmap_anon() more scalable mm/rmap: Convert the struct anon_vma::mutex to an rwsem mm: migrate: Account a transhuge page properly when rate limiting mm: numa: Account for failed allocations and isolations as migration failures mm: numa: Add THP migration for the NUMA working set scanning fault case build fix mm: numa: Add THP migration for the NUMA working set scanning fault case. mm: sched: numa: Delay PTE scanning until a task is scheduled on a new node mm: sched: numa: Control enabling and disabling of NUMA balancing if !SCHED_DEBUG mm: sched: numa: Control enabling and disabling of NUMA balancing mm: sched: Adapt the scanning rate if a NUMA hinting fault does not migrate mm: numa: Use a two-stage filter to restrict pages being migrated for unlikely task<->node relationships mm: numa: migrate: Set last_nid on newly allocated page mm: numa: split_huge_page: Transfer last_nid on tail page mm: numa: Introduce last_nid to the page frame sched: numa: Slowly increase the scanning period as NUMA faults are handled mm: numa: Rate limit setting of pte_numa if node is saturated mm: numa: Rate limit the amount of memory that is migrated between nodes mm: numa: Structures for Migrate On Fault per NUMA migration rate limiting mm: numa: Migrate pages handled during a pmd_numa hinting fault mm: numa: Migrate on reference policy ...
2012-12-14Revert "sched: Update_cfs_shares at period edge"Linus Torvalds
This reverts commit f269ae0469fc882332bdfb5db15d3c1315fe2a10. It turns out it causes a very noticeable interactivity regression with CONFIG_SCHED_AUTOGROUP (test-case: "make -j32" of the kernel in a terminal window, while scrolling in a browser - the autogrouping means that the two end up in separate cgroups, and the browser should be smooth as silk despite the high load). Says Paul Turner: "It seems that the update-throttling on the wake-side is reducing the interactive tasks' ability to preempt. While I suspect the right longer term answer here is force these updates only in the cross-cgroup case; this is less trivial. For this release I believe the right answer is either going to be a revert or restore the updates on the enqueue-side." Reported-by: Linus Torvalds <torvalds@linux-foundation.org> Bisected-by: Mike Galbraith <efault@gmx.de> Acked-by: Paul Turner <pjt@google.com> Acked-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-12-13Merge tag 'kvm-3.8-1' of git://git.kernel.org/pub/scm/virt/kvm/kvmLinus Torvalds
Pull KVM updates from Marcelo Tosatti: "Considerable KVM/PPC work, x86 kvmclock vsyscall support, IA32_TSC_ADJUST MSR emulation, amongst others." Fix up trivial conflict in kernel/sched/core.c due to cross-cpu migration notifier added next to rq migration call-back. * tag 'kvm-3.8-1' of git://git.kernel.org/pub/scm/virt/kvm/kvm: (156 commits) KVM: emulator: fix real mode segment checks in address linearization VMX: remove unneeded enable_unrestricted_guest check KVM: VMX: fix DPL during entry to protected mode x86/kexec: crash_vmclear_local_vmcss needs __rcu kvm: Fix irqfd resampler list walk KVM: VMX: provide the vmclear function and a bitmap to support VMCLEAR in kdump x86/kexec: VMCLEAR VMCSs loaded on all cpus if necessary KVM: MMU: optimize for set_spte KVM: PPC: booke: Get/set guest EPCR register using ONE_REG interface KVM: PPC: bookehv: Add EPCR support in mtspr/mfspr emulation KVM: PPC: bookehv: Add guest computation mode for irq delivery KVM: PPC: Make EPCR a valid field for booke64 and bookehv KVM: PPC: booke: Extend MAS2 EPN mask for 64-bit KVM: PPC: e500: Mask MAS2 EPN high 32-bits in 32/64 tlbwe emulation KVM: PPC: Mask ea's high 32-bits in 32/64 instr emulation KVM: PPC: e500: Add emulation helper for getting instruction ea KVM: PPC: bookehv64: Add support for interrupt handling KVM: PPC: bookehv: Remove GET_VCPU macro from exception handler KVM: PPC: booke: Fix get_tb() compile error on 64-bit KVM: PPC: e500: Silence bogus GCC warning in tlb code ...
2012-12-12Merge branch 'for-3.8' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup Pull cgroup changes from Tejun Heo: "A lot of activities on cgroup side. The big changes are focused on making cgroup hierarchy handling saner. - cgroup_rmdir() had peculiar semantics - it allowed cgroup destruction to be vetoed by individual controllers and tried to drain refcnt synchronously. The vetoing never worked properly and caused good deal of contortions in cgroup. memcg was the last reamining user. Michal Hocko removed the usage and cgroup_rmdir() path has been simplified significantly. This was done in a separate branch so that the memcg people can base further memcg changes on top. - The above allowed cleaning up cgroup lifecycle management and implementation of generic cgroup iterators which are used to improve hierarchy support. - cgroup_freezer updated to allow migration in and out of a frozen cgroup and handle hierarchy. If a cgroup is frozen, all descendant cgroups are frozen. - netcls_cgroup and netprio_cgroup updated to handle hierarchy properly. - Various fixes and cleanups. - Two merge commits. One to pull in memcg and rmdir cleanups (needed to build iterators). The other pulled in cgroup/for-3.7-fixes for device_cgroup fixes so that further device_cgroup patches can be stacked on top." Fixed up a trivial conflict in mm/memcontrol.c as per Tejun (due to commit bea8c150a7 ("memcg: fix hotplugged memory zone oops") in master touching code close to commit 2ef37d3fe4 ("memcg: Simplify mem_cgroup_force_empty_list error handling") in for-3.8) * 'for-3.8' of git://git.kernel.org/pub/scm/linux/kernel/git/tj/cgroup: (65 commits) cgroup: update Documentation/cgroups/00-INDEX cgroup_rm_file: don't delete the uncreated files cgroup: remove subsystem files when remounting cgroup cgroup: use cgroup_addrm_files() in cgroup_clear_directory() cgroup: warn about broken hierarchies only after css_online cgroup: list_del_init() on removed events cgroup: fix lockdep warning for event_control cgroup: move list add after list head initilization netprio_cgroup: allow nesting and inherit config on cgroup creation netprio_cgroup: implement netprio[_set]_prio() helpers netprio_cgroup: use cgroup->id instead of cgroup_netprio_state->prioidx netprio_cgroup: reimplement priomap expansion netprio_cgroup: shorten variable names in extend_netdev_table() netprio_cgroup: simplify write_priomap() netcls_cgroup: move config inheritance to ->css_online() and remove .broken_hierarchy marking cgroup: remove obsolete guarantee from cgroup_task_migrate. cgroup: add cgroup->id cgroup, cpuset: remove cgroup_subsys->post_clone() cgroup: s/CGRP_CLONE_CHILDREN/CGRP_CPUSET_CLONE_CHILDREN/ cgroup: rename ->create/post_create/pre_destroy/destroy() to ->css_alloc/online/offline/free() ...
2012-12-11Merge branch 'sched-core-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull scheduler updates from Ingo Molnar: "The biggest change affects group scheduling: we now track the runnable average on a per-task entity basis, allowing a smoother, exponential decay average based load/weight estimation instead of the previous binary on-the-runqueue/off-the-runqueue load weight method. This will inevitably disturb workloads that were in some sort of borderline balancing state or unstable equilibrium, so an eye has to be kept on regressions. For that reason the new load average is only limited to group scheduling (shares distribution) at the moment (which was also hurting the most from the prior, crude weight calculation and whose scheduling quality wins most from this change) - but we plan to extend this to regular SMP balancing as well in the future, which will simplify and speed up things a bit. Other changes involve ongoing preparatory work to extend NOHZ to the scheduler as well, eventually allowing completely irq-free user-space execution." * 'sched-core-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (33 commits) Revert "sched/autogroup: Fix crash on reboot when autogroup is disabled" cputime: Comment cputime's adjusting code cputime: Consolidate cputime adjustment code cputime: Rename thread_group_times to thread_group_cputime_adjusted cputime: Move thread_group_cputime() to sched code vtime: Warn if irqs aren't disabled on system time accounting APIs vtime: No need to disable irqs on vtime_account() vtime: Consolidate a bit the ctx switch code vtime: Explicitly account pending user time on process tick vtime: Remove the underscore prefix invasion sched/autogroup: Fix crash on reboot when autogroup is disabled cputime: Separate irqtime accounting from generic vtime cputime: Specialize irq vtime hooks kvm: Directly account vtime to system on guest switch vtime: Make vtime_account_system() irqsafe vtime: Gather vtime declarations to their own header file sched: Describe CFS load-balancer sched: Introduce temporary FAIR_GROUP_SCHED dependency for load-tracking sched: Make __update_entity_runnable_avg() fast sched: Update_cfs_shares at period edge ...
2012-12-11Merge branch 'core-rcu-for-linus' of ↵Linus Torvalds
git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip Pull RCU update from Ingo Molnar: "The major features of this tree are: 1. A first version of no-callbacks CPUs. This version prohibits offlining CPU 0, but only when enabled via CONFIG_RCU_NOCB_CPU=y. Relaxing this constraint is in progress, but not yet ready for prime time. These commits were posted to LKML at https://lkml.org/lkml/2012/10/30/724. 2. Changes to SRCU that allows statically initialized srcu_struct structures. These commits were posted to LKML at https://lkml.org/lkml/2012/10/30/296. 3. Restructuring of RCU's debugfs output. These commits were posted to LKML at https://lkml.org/lkml/2012/10/30/341. 4. Additional CPU-hotplug/RCU improvements, posted to LKML at https://lkml.org/lkml/2012/10/30/327. Note that the commit eliminating __stop_machine() was judged to be too-high of risk, so is deferred to 3.9. 5. Changes to RCU's idle interface, most notably a new module parameter that redirects normal grace-period operations to their expedited equivalents. These were posted to LKML at https://lkml.org/lkml/2012/10/30/739. 6. Additional diagnostics for RCU's CPU stall warning facility, posted to LKML at https://lkml.org/lkml/2012/10/30/315. The most notable change reduces the default RCU CPU stall-warning time from 60 seconds to 21 seconds, so that it once again happens sooner than the softlockup timeout. 7. Documentation updates, which were posted to LKML at https://lkml.org/lkml/2012/10/30/280. A couple of late-breaking changes were posted at https://lkml.org/lkml/2012/11/16/634 and https://lkml.org/lkml/2012/11/16/547. 8. Miscellaneous fixes, which were posted to LKML at https://lkml.org/lkml/2012/10/30/309. 9. Finally, a fix for an lockdep-RCU splat was posted to LKML at https://lkml.org/lkml/2012/11/7/486." * 'core-rcu-for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/tip/tip: (49 commits) context_tracking: New context tracking susbsystem sched: Mark RCU reader in sched_show_task() rcu: Separate accounting of callbacks from callback-free CPUs rcu: Add callback-free CPUs rcu: Add documentation for the new rcuexp debugfs trace file rcu: Update documentation for TREE_RCU debugfs tracing rcu: Reduce default RCU CPU stall warning timeout rcu: Fix TINY_RCU rcu_is_cpu_rrupt_from_idle check rcu: Clarify memory-ordering properties of grace-period primitives rcu: Add new rcutorture module parameters to start/end test messages rcu: Remove list_for_each_continue_rcu() rcu: Fix batch-limit size problem rcu: Add tracing for synchronize_sched_expedited() rcu: Remove old debugfs interfaces and also RCU flavor name rcu: split 'rcuhier' to each flavor rcu: split 'rcugp' to each flavor rcu: split 'rcuboost' to each flavor rcu: split 'rcubarrier' to each flavor rcu: Fix tracing formatting rcu: Remove the interface "rcudata.csv" ...
2012-12-11mm: sched: numa: Delay PTE scanning until a task is scheduled on a new nodeMel Gorman
Due to the fact that migrations are driven by the CPU a task is running on there is no point tracking NUMA faults until one task runs on a new node. This patch tracks the first node used by an address space. Until it changes, PTE scanning is disabled and no NUMA hinting faults are trapped. This should help workloads that are short-lived, do not care about NUMA placement or have bound themselves to a single node. This takes advantage of the logic in "mm: sched: numa: Implement slow start for working set sampling" to delay when the checks are made. This will take advantage of processes that set their CPU and node bindings early in their lifetime. It will also potentially allow any initial load balancing to take place. Signed-off-by: Mel Gorman <mgorman@suse.de>
2012-12-11mm: sched: numa: Control enabling and disabling of NUMA balancing if ↵Mel Gorman
!SCHED_DEBUG The "mm: sched: numa: Control enabling and disabling of NUMA balancing" depends on scheduling debug being enabled but it's perfectly legimate to disable automatic NUMA balancing even without this option. This should take care of it. Signed-off-by: Mel Gorman <mgorman@suse.de>
2012-12-11mm: sched: numa: Control enabling and disabling of NUMA balancingMel Gorman
This patch adds Kconfig options and kernel parameters to allow the enabling and disabling of automatic NUMA balancing. The existance of such a switch was and is very important when debugging problems related to transparent hugepages and we should have the same for automatic NUMA placement. Signed-off-by: Mel Gorman <mgorman@suse.de>
2012-12-11mm: sched: Adapt the scanning rate if a NUMA hinting fault does not migrateMel Gorman
The PTE scanning rate and fault rates are two of the biggest sources of system CPU overhead with automatic NUMA placement. Ideally a proper policy would detect if a workload was properly placed, schedule and adjust the PTE scanning rate accordingly. We do not track the necessary information to do that but we at least know if we migrated or not. This patch scans slower if a page was not migrated as the result of a NUMA hinting fault up to sysctl_numa_balancing_scan_period_max which is now higher than the previous default. Once every minute it will reset the scanner in case of phase changes. This is hilariously crude and the numbers are arbitrary. Workloads will converge quite slowly in comparison to what a proper policy should be able to do. On the plus side, we will chew up less CPU for workloads that have no need for automatic balancing. Signed-off-by: Mel Gorman <mgorman@suse.de>
2012-12-11sched: numa: Slowly increase the scanning period as NUMA faults are handledMel Gorman
Currently the rate of scanning for an address space is controlled by the individual tasks. The next scan is simply determined by 2*p->numa_scan_period. The 2*p->numa_scan_period is arbitrary and never changes. At this point there is still no proper policy that decides if a task or process is properly placed. It just scans and assumes the next NUMA fault will place it properly. As it is assumed that pages will get properly placed over time, increase the scan window each time a fault is incurred. This is a big assumption as noted in the comments. It should be noted that changing to p->numa_scan_period will increase system CPU usage because now the scanning rate has effectively doubled. If that is a problem then the min_rate should be made 200ms instead of restoring the 2* logic. Signed-off-by: Mel Gorman <mgorman@suse.de>
2012-12-11mm: numa: Rate limit setting of pte_numa if node is saturatedMel Gorman
If there are a large number of NUMA hinting faults and all of them are resulting in migrations it may indicate that memory is just bouncing uselessly around. NUMA balancing cost is likely exceeding any benefit from locality. Rate limit the PTE updates if the node is migration rate-limited. As noted in the comments, this distorts the NUMA faulting statistics. Signed-off-by: Mel Gorman <mgorman@suse.de>
2012-12-11mm: sched: numa: Implement slow start for working set samplingPeter Zijlstra
Add a 1 second delay before starting to scan the working set of a task and starting to balance it amongst nodes. [ note that before the constant per task WSS sampling rate patch the initial scan would happen much later still, in effect that patch caused this regression. ] The theory is that short-run tasks benefit very little from NUMA placement: they come and go, and they better stick to the node they were started on. As tasks mature and rebalance to other CPUs and nodes, so does their NUMA placement have to change and so does it start to matter more and more. In practice this change fixes an observable kbuild regression: # [ a perf stat --null --repeat 10 test of ten bzImage builds to /dev/shm ] !NUMA: 45.291088843 seconds time elapsed ( +- 0.40% ) 45.154231752 seconds time elapsed ( +- 0.36% ) +NUMA, no slow start: 46.172308123 seconds time elapsed ( +- 0.30% ) 46.343168745 seconds time elapsed ( +- 0.25% ) +NUMA, 1 sec slow start: 45.224189155 seconds time elapsed ( +- 0.25% ) 45.160866532 seconds time elapsed ( +- 0.17% ) and it also fixes an observable perf bench (hackbench) regression: # perf stat --null --repeat 10 perf bench sched messaging -NUMA: -NUMA: 0.246225691 seconds time elapsed ( +- 1.31% ) +NUMA no slow start: 0.252620063 seconds time elapsed ( +- 1.13% ) +NUMA 1sec delay: 0.248076230 seconds time elapsed ( +- 1.35% ) The implementation is simple and straightforward, most of the patch deals with adding the /proc/sys/kernel/numa_balancing_scan_delay_ms tunable knob. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Rik van Riel <riel@redhat.com> [ Wrote the changelog, ran measurements, tuned the default. ] Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Mel Gorman <mgorman@suse.de> Reviewed-by: Rik van Riel <riel@redhat.com>
2012-12-11sched, numa, mm: Count WS scanning against present PTEs, not virtual memory ↵Mel Gorman
ranges By accounting against the present PTEs, scanning speed reflects the actual present (mapped) memory. Suggested-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Rik van Riel <riel@redhat.com> Cc: Mel Gorman <mgorman@suse.de> Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Mel Gorman <mgorman@suse.de>
2012-12-11mm: sched: numa: Implement constant, per task Working Set Sampling (WSS) ratePeter Zijlstra
Previously, to probe the working set of a task, we'd use a very simple and crude method: mark all of its address space PROT_NONE. That method has various (obvious) disadvantages: - it samples the working set at dissimilar rates, giving some tasks a sampling quality advantage over others. - creates performance problems for tasks with very large working sets - over-samples processes with large address spaces but which only very rarely execute Improve that method by keeping a rotating offset into the address space that marks the current position of the scan, and advance it by a constant rate (in a CPU cycles execution proportional manner). If the offset reaches the last mapped address of the mm then it then it starts over at the first address. The per-task nature of the working set sampling functionality in this tree allows such constant rate, per task, execution-weight proportional sampling of the working set, with an adaptive sampling interval/frequency that goes from once per 100ms up to just once per 8 seconds. The current sampling volume is 256 MB per interval. As tasks mature and converge their working set, so does the sampling rate slow down to just a trickle, 256 MB per 8 seconds of CPU time executed. This, beyond being adaptive, also rate-limits rarely executing systems and does not over-sample on overloaded systems. [ In AutoNUMA speak, this patch deals with the effective sampling rate of the 'hinting page fault'. AutoNUMA's scanning is currently rate-limited, but it is also fundamentally single-threaded, executing in the knuma_scand kernel thread, so the limit in AutoNUMA is global and does not scale up with the number of CPUs, nor does it scan tasks in an execution proportional manner. So the idea of rate-limiting the scanning was first implemented in the AutoNUMA tree via a global rate limit. This patch goes beyond that by implementing an execution rate proportional working set sampling rate that is not implemented via a single global scanning daemon. ] [ Dan Carpenter pointed out a possible NULL pointer dereference in the first version of this patch. ] Based-on-idea-by: Andrea Arcangeli <aarcange@redhat.com> Bug-Found-By: Dan Carpenter <dan.carpenter@oracle.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Andrea Arcangeli <aarcange@redhat.com> Cc: Rik van Riel <riel@redhat.com> [ Wrote changelog and fixed bug. ] Signed-off-by: Ingo Molnar <mingo@kernel.org> Signed-off-by: Mel Gorman <mgorman@suse.de> Reviewed-by: Rik van Riel <riel@redhat.com>
2012-12-11mm: numa: Add fault driven placement and migrationPeter Zijlstra
NOTE: This patch is based on "sched, numa, mm: Add fault driven placement and migration policy" but as it throws away all the policy to just leave a basic foundation I had to drop the signed-offs-by. This patch creates a bare-bones method for setting PTEs pte_numa in the context of the scheduler that when faulted later will be faulted onto the node the CPU is running on. In itself this does nothing useful but any placement policy will fundamentally depend on receiving hints on placement from fault context and doing something intelligent about it. Signed-off-by: Mel Gorman <mgorman@suse.de> Acked-by: Rik van Riel <riel@redhat.com>
2012-12-11Revert "sched/autogroup: Fix crash on reboot when autogroup is disabled"Ingo Molnar
This reverts commit 5258f386ea4e8454bc801fb443e8a4217da1947c, because the underlying autogroups bug got fixed upstream in a better way, via: fd8ef11730f1 Revert "sched, autogroup: Stop going ahead if autogroup is disabled" Cc: Mike Galbraith <efault@gmx.de> Cc: Yong Zhang <yong.zhang0@gmail.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: Linus Torvalds <torvalds@linux-foundation.org> Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-12-08Merge tag 'sched-cputime-for-mingo' of ↵Ingo Molnar
git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks into sched/core Pull more cputime cleanups from Frederic Weisbecker: * Get rid of underscores polluting the vtime namespace * Consolidate context switch and tick handling * Improve debuggability by detecting irq unsafe callers Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-12-03Revert "sched, autogroup: Stop going ahead if autogroup is disabled"Mike Galbraith
This reverts commit 800d4d30c8f20bd728e5741a3b77c4859a613f7c. Between commits 8323f26ce342 ("sched: Fix race in task_group()") and 800d4d30c8f2 ("sched, autogroup: Stop going ahead if autogroup is disabled"), autogroup is a wreck. With both applied, all you have to do to crash a box is disable autogroup during boot up, then reboot.. boom, NULL pointer dereference due to commit 800d4d30c8f2 not allowing autogroup to move things, and commit 8323f26ce342 making that the only way to switch runqueues: BUG: unable to handle kernel NULL pointer dereference at (null) IP: [<ffffffff81063ac0>] effective_load.isra.43+0x50/0x90 Pid: 7047, comm: systemd-user-se Not tainted 3.6.8-smp #7 MEDIONPC MS-7502/MS-7502 RIP: effective_load.isra.43+0x50/0x90 Process systemd-user-se (pid: 7047, threadinfo ffff880221dde000, task ffff88022618b3a0) Call Trace: select_task_rq_fair+0x255/0x780 try_to_wake_up+0x156/0x2c0 wake_up_state+0xb/0x10 signal_wake_up+0x28/0x40 complete_signal+0x1d6/0x250 __send_signal+0x170/0x310 send_signal+0x40/0x80 do_send_sig_info+0x47/0x90 group_send_sig_info+0x4a/0x70 kill_pid_info+0x3a/0x60 sys_kill+0x97/0x1a0 ? vfs_read+0x120/0x160 ? sys_read+0x45/0x90 system_call_fastpath+0x16/0x1b Code: 49 0f af 41 50 31 d2 49 f7 f0 48 83 f8 01 48 0f 46 c6 48 2b 07 48 8b bf 40 01 00 00 48 85 ff 74 3a 45 31 c0 48 8b 8f 50 01 00 00 <48> 8b 11 4c 8b 89 80 00 00 00 49 89 d2 48 01 d0 45 8b 59 58 4c RIP [<ffffffff81063ac0>] effective_load.isra.43+0x50/0x90 RSP <ffff880221ddfbd8> CR2: 0000000000000000 Signed-off-by: Mike Galbraith <efault@gmx.de> Acked-by: Ingo Molnar <mingo@kernel.org> Cc: Yong Zhang <yong.zhang0@gmail.com> Cc: Peter Zijlstra <a.p.zijlstra@chello.nl> Cc: stable@vger.kernel.org # 2.6.39+ Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2012-11-30context_tracking: New context tracking susbsystemFrederic Weisbecker
Create a new subsystem that probes on kernel boundaries to keep track of the transitions between level contexts with two basic initial contexts: user or kernel. This is an abstraction of some RCU code that use such tracking to implement its userspace extended quiescent state. We need to pull this up from RCU into this new level of indirection because this tracking is also going to be used to implement an "on demand" generic virtual cputime accounting. A necessary step to shutdown the tick while still accounting the cputime. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: H. Peter Anvin <hpa@zytor.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Li Zhong <zhong@linux.vnet.ibm.com> Cc: Gilad Ben-Yossef <gilad@benyossef.com> Reviewed-by: Steven Rostedt <rostedt@goodmis.org> [ paulmck: fix whitespace error and email address. ] Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2012-11-28cputime: Comment cputime's adjusting codeFrederic Weisbecker
The reason for the scaling and monotonicity correction performed by cputime_adjust() may not be immediately clear to the reviewer. Add some comments to explain what happens there. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
2012-11-28cputime: Consolidate cputime adjustment codeFrederic Weisbecker
task_cputime_adjusted() and thread_group_cputime_adjusted() essentially share the same code. They just don't use the same source: * The first function uses the cputime in the task struct and the previous adjusted snapshot that ensures monotonicity. * The second adds the cputime of all tasks in the group and the previous adjusted snapshot of the whole group from the signal structure. Just consolidate the common code that does the adjustment. These functions just need to fetch the values from the appropriate source. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
2012-11-28cputime: Rename thread_group_times to thread_group_cputime_adjustedFrederic Weisbecker
We have thread_group_cputime() and thread_group_times(). The naming doesn't provide enough information about the difference between these two APIs. To lower the confusion, rename thread_group_times() to thread_group_cputime_adjusted(). This name better suggests that it's a version of thread_group_cputime() that does some stabilization on the raw cputime values. ie here: scale on top of CFS runtime stats and bound lower value for monotonicity. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
2012-11-28cputime: Move thread_group_cputime() to sched codeFrederic Weisbecker
thread_group_cputime() is a general cputime API that is not only used by posix cpu timer. Let's move this helper to sched code. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Ingo Molnar <mingo@kernel.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
2012-11-27sched: add notifier for cross-cpu migrationsMarcelo Tosatti
Originally from Jeremy Fitzhardinge. Acked-by: Ingo Molnar <mingo@redhat.com> Signed-off-by: Marcelo Tosatti <mtosatti@redhat.com>
2012-11-20userns: Kill task_user_nsEric W. Biederman
The task_user_ns function hides the fact that it is getting the user namespace from struct cred on the task. struct cred may go away as soon as the rcu lock is released. This leads to a race where we can dereference a stale user namespace pointer. To make it obvious a struct cred is involved kill task_user_ns. To kill the race modify the users of task_user_ns to only reference the user namespace while the rcu lock is held. Cc: Kees Cook <keescook@chromium.org> Cc: James Morris <james.l.morris@oracle.com> Acked-by: Kees Cook <keescook@chromium.org> Acked-by: Serge Hallyn <serge.hallyn@canonical.com> Signed-off-by: "Eric W. Biederman" <ebiederm@xmission.com>
2012-11-19cgroup: rename ->create/post_create/pre_destroy/destroy() to ↵Tejun Heo
->css_alloc/online/offline/free() Rename cgroup_subsys css lifetime related callbacks to better describe what their roles are. Also, update documentation. Signed-off-by: Tejun Heo <tj@kernel.org> Acked-by: Li Zefan <lizefan@huawei.com>
2012-11-19vtime: No need to disable irqs on vtime_account()Frederic Weisbecker
vtime_account() is only called from irq entry. irqs are always disabled at this point so we can safely remove the irq disabling guards on that function. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Reviewed-by: Steven Rostedt <rostedt@goodmis.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
2012-11-19vtime: Consolidate a bit the ctx switch codeFrederic Weisbecker
On ia64 and powerpc, vtime context switch only consists in flushing system and user pending time, plus a few arch housekeeping. Consolidate that into a generic implementation. s390 is a special case because pending user and system time accounting there is hard to dissociate. So it's keeping its own implementation. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Reviewed-by: Steven Rostedt <rostedt@goodmis.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
2012-11-19vtime: Remove the underscore prefix invasionFrederic Weisbecker
Prepending irq-unsafe vtime APIs with underscores was actually a bad idea as the result is a big mess in the API namespace that is even waiting to be further extended. Also these helpers are always called from irq safe callers except kvm. Just provide a vtime_account_system_irqsafe() for this specific case so that we can remove the underscore prefix on other vtime functions. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Reviewed-by: Steven Rostedt <rostedt@goodmis.org> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
2012-11-18Merge branch 'sched/urgent' into sched/coreIngo Molnar
Merge in fixes before we queue up dependent bits, to avoid conflicts. Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-11-16sched: Mark RCU reader in sched_show_task()Paul E. McKenney
When sched_show_task() is invoked from try_to_freeze_tasks(), there is no RCU read-side critical section, resulting in the following splat: [ 125.780730] =============================== [ 125.780766] [ INFO: suspicious RCU usage. ] [ 125.780804] 3.7.0-rc3+ #988 Not tainted [ 125.780838] ------------------------------- [ 125.780875] /home/rafael/src/linux/kernel/sched/core.c:4497 suspicious rcu_dereference_check() usage! [ 125.780946] [ 125.780946] other info that might help us debug this: [ 125.780946] [ 125.781031] [ 125.781031] rcu_scheduler_active = 1, debug_locks = 0 [ 125.781087] 4 locks held by s2ram/4211: [ 125.781120] #0: (&buffer->mutex){+.+.+.}, at: [<ffffffff811e2acf>] sysfs_write_file+0x3f/0x160 [ 125.781233] #1: (s_active#94){.+.+.+}, at: [<ffffffff811e2b58>] sysfs_write_file+0xc8/0x160 [ 125.781339] #2: (pm_mutex){+.+.+.}, at: [<ffffffff81090a81>] pm_suspend+0x81/0x230 [ 125.781439] #3: (tasklist_lock){.?.?..}, at: [<ffffffff8108feed>] try_to_freeze_tasks+0x2cd/0x3f0 [ 125.781543] [ 125.781543] stack backtrace: [ 125.781584] Pid: 4211, comm: s2ram Not tainted 3.7.0-rc3+ #988 [ 125.781632] Call Trace: [ 125.781662] [<ffffffff810a3c73>] lockdep_rcu_suspicious+0x103/0x140 [ 125.781719] [<ffffffff8107cf21>] sched_show_task+0x121/0x180 [ 125.781770] [<ffffffff8108ffb4>] try_to_freeze_tasks+0x394/0x3f0 [ 125.781823] [<ffffffff810903b5>] freeze_kernel_threads+0x25/0x80 [ 125.781876] [<ffffffff81090b65>] pm_suspend+0x165/0x230 [ 125.781924] [<ffffffff8108fa29>] state_store+0x99/0x100 [ 125.781975] [<ffffffff812f5867>] kobj_attr_store+0x17/0x20 [ 125.782038] [<ffffffff811e2b71>] sysfs_write_file+0xe1/0x160 [ 125.782091] [<ffffffff811667a6>] vfs_write+0xc6/0x180 [ 125.782138] [<ffffffff81166ada>] sys_write+0x5a/0xa0 [ 125.782185] [<ffffffff812ff6ae>] ? trace_hardirqs_on_thunk+0x3a/0x3f [ 125.782242] [<ffffffff81669dd2>] system_call_fastpath+0x16/0x1b This commit therefore adds the needed RCU read-side critical section. Reported-by: "Rafael J. Wysocki" <rjw@sisk.pl> Signed-off-by: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
2012-11-16Merge branches 'urgent.2012.10.27a', 'doc.2012.11.16a', 'fixes.2012.11.13a', ↵Paul E. McKenney
'srcu.2012.10.27a', 'stall.2012.11.13a', 'tracing.2012.11.08a' and 'idle.2012.10.24a' into HEAD urgent.2012.10.27a: Fix for RCU user-mode transition (already in -tip). doc.2012.11.08a: Documentation updates, most notably codifying the memory-barrier guarantees inherent to grace periods. fixes.2012.11.13a: Miscellaneous fixes. srcu.2012.10.27a: Allow statically allocated and initialized srcu_struct structures (courtesy of Lai Jiangshan). stall.2012.11.13a: Add more diagnostic information to RCU CPU stall warnings, also decrease from 60 seconds to 21 seconds. hotplug.2012.11.08a: Minor updates to CPU hotplug handling. tracing.2012.11.08a: Improved debugfs tracing, courtesy of Michael Wang. idle.2012.10.24a: Updates to RCU idle/adaptive-idle handling, including a boot parameter that maps normal grace periods to expedited. Resolved conflict in kernel/rcutree.c due to side-by-side change.
2012-10-30sched/autogroup: Fix crash on reboot when autogroup is disabledMike Galbraith
Due to these two commits: 8323f26ce342 sched: Fix race in task_group() 800d4d30c8f2 sched, autogroup: Stop going ahead if autogroup is disabled ... autogroup scheduling's dynamic knobs are wrecked. With both patches applied, all you have to do to crash a box is disable autogroup during boot up, then reboot.. boom, NULL pointer dereference due to 800d4d30 not allowing autogroup to move things, and 8323f26ce making that the only way to switch runqueues. Remove most of the (dysfunctional) knobs and turn the remaining sched_autogroup_enabled knob readonly. If the user fiddles with cgroups hereafter, once tasks are moved, autogroup won't mess with them again unless they call setsid(). No knobs, no glitz, nada, just a cute little thing folks can turn on if they don't want to muck about with cgroups and/or systemd. Signed-off-by: Mike Galbraith <efault@gmx.de> Cc: Xiaotian Feng <xtfeng@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Xiaotian Feng <dannyfeng@tencent.com> Cc: Linus Torvalds <torvalds@linux-foundation.org> Cc: Andrew Morton <akpm@linux-foundation.org> Cc: Oleg Nesterov <oleg@redhat.com> Cc: <stable@vger.kernel.org> # v3.6 Link: http://lkml.kernel.org/r/1351451963.4999.8.camel@maggy.simpson.net Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-29cputime: Separate irqtime accounting from generic vtimeFrederic Weisbecker
vtime_account() doesn't have the same role in CONFIG_VIRT_CPU_ACCOUNTING and CONFIG_IRQ_TIME_ACCOUNTING. In the first case it handles time accounting in any context. In the second case it only handles irq time accounting. So when vtime_account() is called from outside vtime_account_irq_*() this call is pointless to CONFIG_IRQ_TIME_ACCOUNTING. To fix the confusion, change vtime_account() to irqtime_account_irq() in CONFIG_IRQ_TIME_ACCOUNTING. This way we ensure future account_vtime() calls won't waste useless cycles in the irqtime APIs. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
2012-10-29vtime: Make vtime_account_system() irqsafeFrederic Weisbecker
vtime_account_system() currently has only one caller with vtime_account() which is irq safe. Now we are going to call it from other places like kvm where irqs are not always disabled by the time we account the cputime. So let's make it irqsafe. The arch implementation part is now prefixed with "__". vtime_account_idle() arch implementation is prefixed accordingly to stay consistent. Signed-off-by: Frederic Weisbecker <fweisbec@gmail.com> Cc: Peter Zijlstra <peterz@infradead.org> Cc: Ingo Molnar <mingo@kernel.org> Cc: Thomas Gleixner <tglx@linutronix.de> Cc: Steven Rostedt <rostedt@goodmis.org> Cc: Paul Gortmaker <paul.gortmaker@windriver.com> Cc: Tony Luck <tony.luck@intel.com> Cc: Fenghua Yu <fenghua.yu@intel.com> Cc: Benjamin Herrenschmidt <benh@kernel.crashing.org> Cc: Paul Mackerras <paulus@samba.org> Cc: Martin Schwidefsky <schwidefsky@de.ibm.com> Cc: Heiko Carstens <heiko.carstens@de.ibm.com>
2012-10-24sched: Describe CFS load-balancerPeter Zijlstra
Add some scribbles on how and why the load-balancer works.. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/1341316406.23484.64.camel@twins Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-24sched: Introduce temporary FAIR_GROUP_SCHED dependency for load-trackingPaul Turner
While per-entity load-tracking is generally useful, beyond computing shares distribution, e.g. runnable based load-balance (in progress), governors, power-management, etc. These facilities are not yet consumers of this data. This may be trivially reverted when the information is required; but avoid paying the overhead for calculations we will not use until then. Signed-off-by: Paul Turner <pjt@google.com> Reviewed-by: Ben Segall <bsegall@google.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/20120823141507.422162369@google.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-24sched: Make __update_entity_runnable_avg() fastPaul Turner
__update_entity_runnable_avg forms the core of maintaining an entity's runnable load average. In this function we charge the accumulated run-time since last update and handle appropriate decay. In some cases, e.g. a waking task, this time interval may be much larger than our period unit. Fortunately we can exploit some properties of our series to perform decay for a blocked update in constant time and account the contribution for a running update in essentially-constant* time. [*]: For any running entity they should be performing updates at the tick which gives us a soft limit of 1 jiffy between updates, and we can compute up to a 32 jiffy update in a single pass. C program to generate the magic constants in the arrays: #include <math.h> #include <stdio.h> #define N 32 #define WMULT_SHIFT 32 const long WMULT_CONST = ((1UL << N) - 1); double y; long runnable_avg_yN_inv[N]; void calc_mult_inv() { int i; double yn = 0; printf("inverses\n"); for (i = 0; i < N; i++) { yn = (double)WMULT_CONST * pow(y, i); runnable_avg_yN_inv[i] = yn; printf("%2d: 0x%8lx\n", i, runnable_avg_yN_inv[i]); } printf("\n"); } long mult_inv(long c, int n) { return (c * runnable_avg_yN_inv[n]) >> WMULT_SHIFT; } void calc_yn_sum(int n) { int i; double sum = 0, sum_fl = 0, diff = 0; /* * We take the floored sum to ensure the sum of partial sums is never * larger than the actual sum. */ printf("sum y^n\n"); printf(" %8s %8s %8s\n", "exact", "floor", "error"); for (i = 1; i <= n; i++) { sum = (y * sum + y * 1024); sum_fl = floor(y * sum_fl+ y * 1024); printf("%2d: %8.0f %8.0f %8.0f\n", i, sum, sum_fl, sum_fl - sum); } printf("\n"); } void calc_conv(long n) { long old_n; int i = -1; printf("convergence (LOAD_AVG_MAX, LOAD_AVG_MAX_N)\n"); do { old_n = n; n = mult_inv(n, 1) + 1024; i++; } while (n != old_n); printf("%d> %ld\n", i - 1, n); printf("\n"); } void main() { y = pow(0.5, 1/(double)N); calc_mult_inv(); calc_conv(1024); calc_yn_sum(N); } [ Compile with -lm ] Signed-off-by: Paul Turner <pjt@google.com> Reviewed-by: Ben Segall <bsegall@google.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/20120823141507.277808946@google.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-24sched: Update_cfs_shares at period edgePaul Turner
Now that our measurement intervals are small (~1ms) we can amortize the posting of update_shares() to be about each period overflow. This is a large cost saving for frequently switching tasks. Signed-off-by: Paul Turner <pjt@google.com> Reviewed-by: Ben Segall <bsegall@google.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/20120823141507.200772172@google.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-24sched: Refactor update_shares_cpu() -> update_blocked_avgs()Paul Turner
Now that running entities maintain their own load-averages the work we must do in update_shares() is largely restricted to the periodic decay of blocked entities. This allows us to be a little less pessimistic regarding our occupancy on rq->lock and the associated rq->clock updates required. Signed-off-by: Paul Turner <pjt@google.com> Reviewed-by: Ben Segall <bsegall@google.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/20120823141507.133999170@google.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-24sched: Replace update_shares weight distribution with per-entity computationPaul Turner
Now that the machinery in place is in place to compute contributed load in a bottom up fashion; replace the shares distribution code within update_shares() accordingly. Signed-off-by: Paul Turner <pjt@google.com> Reviewed-by: Ben Segall <bsegall@google.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/20120823141507.061208672@google.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-24sched: Maintain runnable averages across throttled periodsPaul Turner
With bandwidth control tracked entities may cease execution according to user specified bandwidth limits. Charging this time as either throttled or blocked however, is incorrect and would falsely skew in either direction. What we actually want is for any throttled periods to be "invisible" to load-tracking as they are removed from the system for that interval and contribute normally otherwise. Do this by moderating the progression of time to omit any periods in which the entity belonged to a throttled hierarchy. Signed-off-by: Paul Turner <pjt@google.com> Reviewed-by: Ben Segall <bsegall@google.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/20120823141506.998912151@google.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-24sched: Normalize tg load contributions against runnable timePaul Turner
Entities of equal weight should receive equitable distribution of cpu time. This is challenging in the case of a task_group's shares as execution may be occurring on multiple cpus simultaneously. To handle this we divide up the shares into weights proportionate with the load on each cfs_rq. This does not however, account for the fact that the sum of the parts may be less than one cpu and so we need to normalize: load(tg) = min(runnable_avg(tg), 1) * tg->shares Where runnable_avg is the aggregate time in which the task_group had runnable children. Signed-off-by: Paul Turner <pjt@google.com> Reviewed-by: Ben Segall <bsegall@google.com>. Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/20120823141506.930124292@google.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-24sched: Compute load contribution by a group entityPaul Turner
Unlike task entities who have a fixed weight, group entities instead own a fraction of their parenting task_group's shares as their contributed weight. Compute this fraction so that we can correctly account hierarchies and shared entity nodes. Signed-off-by: Paul Turner <pjt@google.com> Reviewed-by: Ben Segall <bsegall@google.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/20120823141506.855074415@google.com Signed-off-by: Ingo Molnar <mingo@kernel.org>
2012-10-24sched: Aggregate total task_group loadPaul Turner
Maintain a global running sum of the average load seen on each cfs_rq belonging to each task group so that it may be used in calculating an appropriate shares:weight distribution. Signed-off-by: Paul Turner <pjt@google.com> Reviewed-by: Ben Segall <bsegall@google.com> Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl> Link: http://lkml.kernel.org/r/20120823141506.792901086@google.com Signed-off-by: Ingo Molnar <mingo@kernel.org>