Tetsuo Handa f44666b046 mm,oom: speed up select_bad_process() loop ... Since commit 3a5dda7a17 ("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>		2016-05-20 17:58:30 -07:00
..
acpi	Merge branches 'acpi-pci', 'acpi-misc' and 'acpi-tools'	2016-05-16 16:45:48 +02:00
asm-generic	Merge branch 'akpm' (patches from Andrew)	2016-05-19 20:00:06 -07:00
clocksource
crypto	Merge branch 'next' of git://git.kernel.org/pub/scm/linux/kernel/git/jmorris/linux-security	2016-05-19 09:21:36 -07:00
drm
dt-bindings	- New Drivers	2016-05-20 11:10:24 -07:00
keys
kvm
linux	mm,oom: speed up select_bad_process() loop	2016-05-20 17:58:30 -07:00
math-emu
media
memory
misc
net	switchdev: pass pointer to fib_info instead of copy	2016-05-17 13:58:49 -04:00
pcmcia
ras
rdma
rxrpc
scsi
soc	ARC updates for 4.7-rc1	2016-05-19 09:46:18 -07:00
sound	ASoC: Updates for v4.7	2016-05-16 14:59:00 +02:00
target
trace	mm, compaction: distinguish between full and partial COMPACT_COMPLETE	2016-05-20 17:58:30 -07:00
uapi	Merge branch 'i2c/for-4.7' of git://git.kernel.org/pub/scm/linux/kernel/git/wsa/linux	2016-05-19 17:48:12 -07:00
video
xen
Kbuild