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authorIngo Molnar <mingo@elte.hu>2005-08-01 13:39:13 +0200
committerLinus Torvalds <torvalds@g5.osdl.org>2005-08-01 10:03:56 -0700
commit6cb54819d7b1867053e2dfd8c0ca3a8dc65a7eff (patch)
tree1a1422dc2e103fe92dd86bfa26b8b39b3f2413d5
parent5d546f54324e04747e82ccbb4ea85f54bdcacd6d (diff)
downloadconfigs-6cb54819d7b1867053e2dfd8c0ca3a8dc65a7eff.tar.gz
[PATCH] remove sys_set_zone_reclaim()
This removes sys_set_zone_reclaim() for now. While i'm sure Martin is trying to solve a real problem, we must not hard-code an incomplete and insufficient approach into a syscall, because syscalls are pretty much for eternity. I am quite strongly convinced that this syscall must not hit v2.6.13 in its current form. Firstly, the syscall lacks basic syscall design: e.g. it allows the global setting of VM policy for unprivileged users. (!) [ Imagine an Oracle installation and a SAP installation on the same NUMA box fighting over the 'optimal' setting for this flag. What will they do? Will they try to set the flag to their own preferred value every second or so? ] Secondly, it was added based on a single datapoint from Martin: http://marc.theaimsgroup.com/?l=linux-mm&m=111763597218177&w=2 where Martin characterizes the numbers the following way: ' Run-to-run variability for "make -j" is huge, so these numbers aren't terribly useful except to see that with reclaim the benchmark still finishes in a reasonable amount of time. ' in other words: the fundamental problem has likely not been solved, only a tendential move into the right direction has been observed, and a handful of numbers were picked out of a set of hugely variable results, without showing the variability data. How much variance is there run-to-run? I'd really suggest to first walk the walk and see what's needed to get stable & predictable kernel compilation numbers on that NUMA box, before adding random syscalls to tune a particular aspect of the VM ... which approach might not even matter once the whole picture has been analyzed and understood! The third, most important point is that the syscall exposes VM tuning internals in a completely unstructured way. What sense does it make to have a _GLOBAL_ per-node setting for 'should we go to another node for reclaim'? If then it might make sense to do this per-app, via numalib or so. The change is minimalistic in that it doesnt remove the syscall and the underlying infrastructure changes, only the user-visible changes. We could perhaps add a CAP_SYS_ADMIN-only sysctl for this hack, a'ka /proc/sys/vm/swappiness, but even that looks quite counterproductive when the generic approach is that we are trying to reduce the number of external factors in the VM balance picture. Signed-off-by: Ingo Molnar <mingo@elte.hu> Signed-off-by: Linus Torvalds <torvalds@osdl.org>
-rw-r--r--arch/i386/kernel/syscall_table.S2
-rw-r--r--arch/ia64/kernel/entry.S2
-rw-r--r--kernel/sys_ni.c1
3 files changed, 2 insertions, 3 deletions
diff --git a/arch/i386/kernel/syscall_table.S b/arch/i386/kernel/syscall_table.S
index 468500a7e89..9b21a31d4f4 100644
--- a/arch/i386/kernel/syscall_table.S
+++ b/arch/i386/kernel/syscall_table.S
@@ -251,7 +251,7 @@ ENTRY(sys_call_table)
.long sys_io_submit
.long sys_io_cancel
.long sys_fadvise64 /* 250 */
- .long sys_set_zone_reclaim
+ .long sys_ni_syscall
.long sys_exit_group
.long sys_lookup_dcookie
.long sys_epoll_create
diff --git a/arch/ia64/kernel/entry.S b/arch/ia64/kernel/entry.S
index 66946f3fdac..9be53e1ea40 100644
--- a/arch/ia64/kernel/entry.S
+++ b/arch/ia64/kernel/entry.S
@@ -1573,7 +1573,7 @@ sys_call_table:
data8 sys_keyctl
data8 sys_ioprio_set
data8 sys_ioprio_get // 1275
- data8 sys_set_zone_reclaim
+ data8 sys_ni_syscall
data8 sys_inotify_init
data8 sys_inotify_add_watch
data8 sys_inotify_rm_watch
diff --git a/kernel/sys_ni.c b/kernel/sys_ni.c
index 42b40ae5ead..1ab2370e2ef 100644
--- a/kernel/sys_ni.c
+++ b/kernel/sys_ni.c
@@ -79,7 +79,6 @@ cond_syscall(sys_request_key);
cond_syscall(sys_keyctl);
cond_syscall(compat_sys_keyctl);
cond_syscall(compat_sys_socketcall);
-cond_syscall(sys_set_zone_reclaim);
cond_syscall(sys_inotify_init);
cond_syscall(sys_inotify_add_watch);
cond_syscall(sys_inotify_rm_watch);