aboutsummaryrefslogtreecommitdiff
path: root/kernel/sched/fair.c
diff options
context:
space:
mode:
authorLinus Torvalds <torvalds@linux-foundation.org>2012-12-16 14:33:25 -0800
committerLinus Torvalds <torvalds@linux-foundation.org>2012-12-16 15:18:08 -0800
commit3d59eebc5e137bd89c6351e4c70e90ba1d0dc234 (patch)
treeb4ddfd0b057454a7437a3b4e3074a3b8b4b03817 /kernel/sched/fair.c
parent11520e5e7c1855fc3bf202bb3be35a39d9efa034 (diff)
parent4fc3f1d66b1ef0d7b8dc11f4ff1cc510f78b37d6 (diff)
downloadlinaro-lsk-3d59eebc5e137bd89c6351e4c70e90ba1d0dc234.tar.gz
Merge tag 'balancenuma-v11' of 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 ...
Diffstat (limited to 'kernel/sched/fair.c')
-rw-r--r--kernel/sched/fair.c227
1 files changed, 227 insertions, 0 deletions
diff --git a/kernel/sched/fair.c b/kernel/sched/fair.c
index 756f9f9e854..9af5af979a1 100644
--- a/kernel/sched/fair.c
+++ b/kernel/sched/fair.c
@@ -26,6 +26,9 @@
#include <linux/slab.h>
#include <linux/profile.h>
#include <linux/interrupt.h>
+#include <linux/mempolicy.h>
+#include <linux/migrate.h>
+#include <linux/task_work.h>
#include <trace/events/sched.h>
@@ -774,6 +777,227 @@ update_stats_curr_start(struct cfs_rq *cfs_rq, struct sched_entity *se)
* Scheduling class queueing methods:
*/
+#ifdef CONFIG_NUMA_BALANCING
+/*
+ * numa task sample period in ms
+ */
+unsigned int sysctl_numa_balancing_scan_period_min = 100;
+unsigned int sysctl_numa_balancing_scan_period_max = 100*50;
+unsigned int sysctl_numa_balancing_scan_period_reset = 100*600;
+
+/* Portion of address space to scan in MB */
+unsigned int sysctl_numa_balancing_scan_size = 256;
+
+/* Scan @scan_size MB every @scan_period after an initial @scan_delay in ms */
+unsigned int sysctl_numa_balancing_scan_delay = 1000;
+
+static void task_numa_placement(struct task_struct *p)
+{
+ int seq = ACCESS_ONCE(p->mm->numa_scan_seq);
+
+ if (p->numa_scan_seq == seq)
+ return;
+ p->numa_scan_seq = seq;
+
+ /* FIXME: Scheduling placement policy hints go here */
+}
+
+/*
+ * Got a PROT_NONE fault for a page on @node.
+ */
+void task_numa_fault(int node, int pages, bool migrated)
+{
+ struct task_struct *p = current;
+
+ if (!sched_feat_numa(NUMA))
+ return;
+
+ /* FIXME: Allocate task-specific structure for placement policy here */
+
+ /*
+ * If pages are properly placed (did not migrate) then scan slower.
+ * This is reset periodically in case of phase changes
+ */
+ if (!migrated)
+ p->numa_scan_period = min(sysctl_numa_balancing_scan_period_max,
+ p->numa_scan_period + jiffies_to_msecs(10));
+
+ task_numa_placement(p);
+}
+
+static void reset_ptenuma_scan(struct task_struct *p)
+{
+ ACCESS_ONCE(p->mm->numa_scan_seq)++;
+ p->mm->numa_scan_offset = 0;
+}
+
+/*
+ * The expensive part of numa migration is done from task_work context.
+ * Triggered from task_tick_numa().
+ */
+void task_numa_work(struct callback_head *work)
+{
+ unsigned long migrate, next_scan, now = jiffies;
+ struct task_struct *p = current;
+ struct mm_struct *mm = p->mm;
+ struct vm_area_struct *vma;
+ unsigned long start, end;
+ long pages;
+
+ WARN_ON_ONCE(p != container_of(work, struct task_struct, numa_work));
+
+ work->next = work; /* protect against double add */
+ /*
+ * Who cares about NUMA placement when they're dying.
+ *
+ * NOTE: make sure not to dereference p->mm before this check,
+ * exit_task_work() happens _after_ exit_mm() so we could be called
+ * without p->mm even though we still had it when we enqueued this
+ * work.
+ */
+ if (p->flags & PF_EXITING)
+ return;
+
+ /*
+ * We do not care about task placement until a task runs on a node
+ * other than the first one used by the address space. This is
+ * largely because migrations are driven by what CPU the task
+ * is running on. If it's never scheduled on another node, it'll
+ * not migrate so why bother trapping the fault.
+ */
+ if (mm->first_nid == NUMA_PTE_SCAN_INIT)
+ mm->first_nid = numa_node_id();
+ if (mm->first_nid != NUMA_PTE_SCAN_ACTIVE) {
+ /* Are we running on a new node yet? */
+ if (numa_node_id() == mm->first_nid &&
+ !sched_feat_numa(NUMA_FORCE))
+ return;
+
+ mm->first_nid = NUMA_PTE_SCAN_ACTIVE;
+ }
+
+ /*
+ * Reset the scan period if enough time has gone by. Objective is that
+ * scanning will be reduced if pages are properly placed. As tasks
+ * can enter different phases this needs to be re-examined. Lacking
+ * proper tracking of reference behaviour, this blunt hammer is used.
+ */
+ migrate = mm->numa_next_reset;
+ if (time_after(now, migrate)) {
+ p->numa_scan_period = sysctl_numa_balancing_scan_period_min;
+ next_scan = now + msecs_to_jiffies(sysctl_numa_balancing_scan_period_reset);
+ xchg(&mm->numa_next_reset, next_scan);
+ }
+
+ /*
+ * Enforce maximal scan/migration frequency..
+ */
+ migrate = mm->numa_next_scan;
+ if (time_before(now, migrate))
+ return;
+
+ if (p->numa_scan_period == 0)
+ p->numa_scan_period = sysctl_numa_balancing_scan_period_min;
+
+ next_scan = now + msecs_to_jiffies(p->numa_scan_period);
+ if (cmpxchg(&mm->numa_next_scan, migrate, next_scan) != migrate)
+ return;
+
+ /*
+ * Do not set pte_numa if the current running node is rate-limited.
+ * This loses statistics on the fault but if we are unwilling to
+ * migrate to this node, it is less likely we can do useful work
+ */
+ if (migrate_ratelimited(numa_node_id()))
+ return;
+
+ start = mm->numa_scan_offset;
+ pages = sysctl_numa_balancing_scan_size;
+ pages <<= 20 - PAGE_SHIFT; /* MB in pages */
+ if (!pages)
+ return;
+
+ down_read(&mm->mmap_sem);
+ vma = find_vma(mm, start);
+ if (!vma) {
+ reset_ptenuma_scan(p);
+ start = 0;
+ vma = mm->mmap;
+ }
+ for (; vma; vma = vma->vm_next) {
+ if (!vma_migratable(vma))
+ continue;
+
+ /* Skip small VMAs. They are not likely to be of relevance */
+ if (((vma->vm_end - vma->vm_start) >> PAGE_SHIFT) < HPAGE_PMD_NR)
+ continue;
+
+ do {
+ start = max(start, vma->vm_start);
+ end = ALIGN(start + (pages << PAGE_SHIFT), HPAGE_SIZE);
+ end = min(end, vma->vm_end);
+ pages -= change_prot_numa(vma, start, end);
+
+ start = end;
+ if (pages <= 0)
+ goto out;
+ } while (end != vma->vm_end);
+ }
+
+out:
+ /*
+ * It is possible to reach the end of the VMA list but the last few VMAs are
+ * not guaranteed to the vma_migratable. If they are not, we would find the
+ * !migratable VMA on the next scan but not reset the scanner to the start
+ * so check it now.
+ */
+ if (vma)
+ mm->numa_scan_offset = start;
+ else
+ reset_ptenuma_scan(p);
+ up_read(&mm->mmap_sem);
+}
+
+/*
+ * Drive the periodic memory faults..
+ */
+void task_tick_numa(struct rq *rq, struct task_struct *curr)
+{
+ struct callback_head *work = &curr->numa_work;
+ u64 period, now;
+
+ /*
+ * We don't care about NUMA placement if we don't have memory.
+ */
+ if (!curr->mm || (curr->flags & PF_EXITING) || work->next != work)
+ return;
+
+ /*
+ * Using runtime rather than walltime has the dual advantage that
+ * we (mostly) drive the selection from busy threads and that the
+ * task needs to have done some actual work before we bother with
+ * NUMA placement.
+ */
+ now = curr->se.sum_exec_runtime;
+ period = (u64)curr->numa_scan_period * NSEC_PER_MSEC;
+
+ if (now - curr->node_stamp > period) {
+ if (!curr->node_stamp)
+ curr->numa_scan_period = sysctl_numa_balancing_scan_period_min;
+ curr->node_stamp = now;
+
+ if (!time_before(jiffies, curr->mm->numa_next_scan)) {
+ init_task_work(work, task_numa_work); /* TODO: move this into sched_fork() */
+ task_work_add(curr, work, true);
+ }
+ }
+}
+#else
+static void task_tick_numa(struct rq *rq, struct task_struct *curr)
+{
+}
+#endif /* CONFIG_NUMA_BALANCING */
+
static void
account_entity_enqueue(struct cfs_rq *cfs_rq, struct sched_entity *se)
{
@@ -5501,6 +5725,9 @@ static void task_tick_fair(struct rq *rq, struct task_struct *curr, int queued)
entity_tick(cfs_rq, se, queued);
}
+ if (sched_feat_numa(NUMA))
+ task_tick_numa(rq, curr);
+
update_rq_runnable_avg(rq, 1);
}