diff options
| author |   Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> | 2016-05-20 16:57:27 -0700 |
|---|---|---|
| committer |   Linus Torvalds <torvalds@linux-foundation.org> | 2016-05-20 17:58:30 -0700 |
| commit | f44666b04605d1c7fd94ab90b7ccf633e7eff228 (patch) | |
| tree | 70dce12a369be67059e1d51c4aee357261200b3f /include | |
| parent | oom: consider multi-threaded tasks in task_will_free_mem (diff) | |
| download | linux-dev-f44666b04605d1c7fd94ab90b7ccf633e7eff228.tar.xz linux-dev-f44666b04605d1c7fd94ab90b7ccf633e7eff228.zip | |
mm,oom: speed up select_bad_process() loop
Since commit 3a5dda7a17cf ("oom: prevent unnecessary oom kills or kernel
panics"), select_bad_process() is using for_each_process_thread().
Since oom_unkillable_task() scans all threads in the caller's thread
group and oom_task_origin() scans signal_struct of the caller's thread
group, we don't need to call oom_unkillable_task() and oom_task_origin()
on each thread. Also, since !mm test will be done later at
oom_badness(), we don't need to do !mm test on each thread. Therefore,
we only need to do TIF_MEMDIE test on each thread.
Although the original code was correct it was quite inefficient because
each thread group was scanned num_threads times which can be a lot
especially with processes with many threads. Even though the OOM is
extremely cold path it is always good to be as effective as possible
when we are inside rcu_read_lock() - aka unpreemptible context.
If we track number of TIF_MEMDIE threads inside signal_struct, we don't
need to do TIF_MEMDIE test on each thread. This will allow
select_bad_process() to use for_each_process().
This patch adds a counter to signal_struct for tracking how many
TIF_MEMDIE threads are in a given thread group, and check it at
oom_scan_process_thread() so that select_bad_process() can use
for_each_process() rather than for_each_process_thread().
[mhocko@suse.com: do not blow the signal_struct size]
Link: http://lkml.kernel.org/r/20160520075035.GF19172@dhcp22.suse.cz
Link: http://lkml.kernel.org/r/201605182230.IDC73435.MVSOHLFOQFOJtF@I-love.SAKURA.ne.jp
Signed-off-by: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp>
Acked-by: Michal Hocko <mhocko@suse.com>
Cc: David Rientjes <rientjes@google.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Diffstat (limited to 'include')
| -rw-r--r-- | include/linux/sched.h | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/include/linux/sched.h b/include/linux/sched.h index 479e3cade7e9..01fe1bb68754 100644 --- a/include/linux/sched.h +++ b/include/linux/sched.h @@ -669,6 +669,7 @@ struct signal_struct { atomic_t sigcnt; atomic_t live; int nr_threads; + atomic_t oom_victims; /* # of TIF_MEDIE threads in this thread group */ struct list_head thread_head; wait_queue_head_t wait_chldexit; /* for wait4() */ |