memcg: handle panic_on_oom=always case (daaf1e68) · Commits · 戴 / test

Presently, if panic_on_oom=2, the whole system panics even if the oom happend in some special situation (as cpuset, mempolicy....). Then, panic_on_oom=2 means painc_on_oom_always. Now, memcg doesn't check panic_on_oom flag. This patch adds a check. BTW, how it's useful ? kdump+panic_on_oom=2 is the last tool to investigate what happens in oom-ed system. When a task is killed, the sysytem recovers and there will be few hint to know what happnes. In mission critical system, oom should never happen. Then, panic_on_oom=2+kdump is useful to avoid next OOM by knowing precise information via snapshot. TODO: - For memcg, it's for isolate system's memory usage, oom-notiifer and freeze_at_oom (or rest_at_oom) should be implemented. Then, management daemon can do similar jobs (as kdump) or taking snapshot per cgroup. Signed-off-by:

KAMEZAWA Hiroyuki <kamezawa.hiroyu@jp.fujitsu.com> Cc: Balbir Singh <balbir@linux.vnet.ibm.com> Cc: David Rientjes <rientjes@google.com> Cc: Nick Piggin <npiggin@suse.de> Reviewed-by:

Daisuke Nishimura <nishimura@mxp.nes.nec.co.jp> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

Documentation/cgroups/memory.txt

+4 −1

Original line number	Diff line number	Diff line
		@@ -182,6 +182,8 @@ list.
		NOTE: Reclaim does not work for the root cgroup, since we cannot set any
		limits on the root cgroup.

		Note2: When panic_on_oom is set to "2", the whole system will panic.

		2. Locking

		The memory controller uses the following hierarchy
		@@ -379,7 +381,8 @@ The feature can be disabled by
		NOTE1: Enabling/disabling will fail if the cgroup already has other
		cgroups created below it.

		NOTE2: This feature can be enabled/disabled per subtree.
		NOTE2: When panic_on_oom is set to "2", the whole system will panic in
		case of an oom event in any cgroup.

		7. Soft limits

Documentation/sysctl/vm.txt

+4 −1

Original line number	Diff line number	Diff line
		@@ -573,11 +573,14 @@ Because other nodes' memory may be free. This means system total status
		may be not fatal yet.

		If this is set to 2, the kernel panics compulsorily even on the
		above-mentioned.
		above-mentioned. Even oom happens under memory cgroup, the whole
		system panics.

		The default value is 0.
		1 and 2 are for failover of clustering. Please select either
		according to your policy of failover.
		panic_on_oom=2+kdump gives you very strong tool to investigate
		why oom happens. You can get snapshot.

		=============================================================

mm/oom_kill.c

+2 −0

Original line number	Diff line number	Diff line
		@@ -473,6 +473,8 @@ void mem_cgroup_out_of_memory(struct mem_cgroup *mem, gfp_t gfp_mask)
		unsigned long points = 0;
		struct task_struct *p;

		if (sysctl_panic_on_oom == 2)
		panic("out of memory(memcg). panic_on_oom is selected.\n");
		read_lock(&tasklist_lock);
		retry:
		p = select_bad_process(&points, mem);

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