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Date: Tue, 23 May 2017 14:05:53 +0300
From: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
To: Michal Hocko <mhocko@...nel.org>
Cc: linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
Tejun Heo <tj@...nel.org>, cgroups@...r.kernel.org,
linux-kernel@...r.kernel.org, Vlastimil Babka <vbabka@...e.cz>
Subject: Re: [PATCH] mm/oom_kill: count global and memory cgroup oom kills
On 23.05.2017 10:27, Michal Hocko wrote:
> On Fri 19-05-17 17:22:30, Konstantin Khlebnikov wrote:
>> Show count of global oom killer invocations in /proc/vmstat and
>> count of oom kills inside memory cgroup in knob "memory.events"
>> (in memory.oom_control for v1 cgroup).
>>
>> Also describe difference between "oom" and "oom_kill" in memory
>> cgroup documentation. Currently oom in memory cgroup kills tasks
>> iff shortage has happened inside page fault.
>>
>> These counters helps in monitoring oom kills - for now
>> the only way is grepping for magic words in kernel log.
>
> Have you considered adding memcg's oom alternative for the global case
> as well. It would be useful to see how many times we hit the OOM
> condition without killing anything. That could help debugging issues
> when the OOM killer cannot be invoked (e.g. GFP_NO{FS,IO} contextx)
> and the system cannot get out of the oom situation.
I think present warn_alloc() should be enough for debugging,
maybe it should taint kernel in some cases to give a hint for future warnings/bugs.
>
>> Signed-off-by: Konstantin Khlebnikov <khlebnikov@...dex-team.ru>
>
> Acked-by: Michal Hocko <mhocko@...e.com>
>
>> ---
>> Documentation/cgroup-v2.txt | 12 +++++++++++-
>> include/linux/memcontrol.h | 1 +
>> include/linux/vm_event_item.h | 1 +
>> mm/memcontrol.c | 2 ++
>> mm/oom_kill.c | 6 ++++++
>> mm/vmstat.c | 1 +
>> 6 files changed, 22 insertions(+), 1 deletion(-)
>>
>> diff --git a/Documentation/cgroup-v2.txt b/Documentation/cgroup-v2.txt
>> index dc5e2dcdbef4..a742008d76aa 100644
>> --- a/Documentation/cgroup-v2.txt
>> +++ b/Documentation/cgroup-v2.txt
>> @@ -830,9 +830,19 @@ PAGE_SIZE multiple when read back.
>>
>> oom
>>
>> + The number of time the cgroup's memory usage was
>> + reached the limit and allocation was about to fail.
>> + Result could be oom kill, -ENOMEM from any syscall or
>> + completely ignored in cases like disk readahead.
>> + For now oom in memory cgroup kills tasks iff shortage
>> + has happened inside page fault.
>> +
>> + oom_kill
>> +
>> The number of times the OOM killer has been invoked in
>> the cgroup. This may not exactly match the number of
>> - processes killed but should generally be close.
>> + processes killed but should generally be close: each
>> + invocation could kill several processes at once.
>>
>> memory.stat
>>
>> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
>> index 899949bbb2f9..2cdcebb78b58 100644
>> --- a/include/linux/memcontrol.h
>> +++ b/include/linux/memcontrol.h
>> @@ -55,6 +55,7 @@ enum memcg_event_item {
>> MEMCG_HIGH,
>> MEMCG_MAX,
>> MEMCG_OOM,
>> + MEMCG_OOM_KILL,
>> MEMCG_NR_EVENTS,
>> };
>>
>> diff --git a/include/linux/vm_event_item.h b/include/linux/vm_event_item.h
>> index d84ae90ccd5c..1707e0a7d943 100644
>> --- a/include/linux/vm_event_item.h
>> +++ b/include/linux/vm_event_item.h
>> @@ -41,6 +41,7 @@ enum vm_event_item { PGPGIN, PGPGOUT, PSWPIN, PSWPOUT,
>> KSWAPD_LOW_WMARK_HIT_QUICKLY, KSWAPD_HIGH_WMARK_HIT_QUICKLY,
>> PAGEOUTRUN, PGROTATED,
>> DROP_PAGECACHE, DROP_SLAB,
>> + OOM_KILL,
>> #ifdef CONFIG_NUMA_BALANCING
>> NUMA_PTE_UPDATES,
>> NUMA_HUGE_PTE_UPDATES,
>> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
>> index 94172089f52f..416024837b81 100644
>> --- a/mm/memcontrol.c
>> +++ b/mm/memcontrol.c
>> @@ -3574,6 +3574,7 @@ static int mem_cgroup_oom_control_read(struct seq_file *sf, void *v)
>>
>> seq_printf(sf, "oom_kill_disable %d\n", memcg->oom_kill_disable);
>> seq_printf(sf, "under_oom %d\n", (bool)memcg->under_oom);
>> + seq_printf(sf, "oom_kill %lu\n", memcg_sum_events(memcg, MEMCG_OOM_KILL));
>> return 0;
>> }
>>
>> @@ -5165,6 +5166,7 @@ static int memory_events_show(struct seq_file *m, void *v)
>> seq_printf(m, "high %lu\n", memcg_sum_events(memcg, MEMCG_HIGH));
>> seq_printf(m, "max %lu\n", memcg_sum_events(memcg, MEMCG_MAX));
>> seq_printf(m, "oom %lu\n", memcg_sum_events(memcg, MEMCG_OOM));
>> + seq_printf(m, "oom_kill %lu\n", memcg_sum_events(memcg, MEMCG_OOM_KILL));
>>
>> return 0;
>> }
>> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
>> index 04c9143a8625..c50bff3c3409 100644
>> --- a/mm/oom_kill.c
>> +++ b/mm/oom_kill.c
>> @@ -873,6 +873,12 @@ static void oom_kill_process(struct oom_control *oc, const char *message)
>> victim = p;
>> }
>>
>> + /* Raise event before sending signal: reaper must see this */
>> + if (!is_memcg_oom(oc))
>> + count_vm_event(OOM_KILL);
>> + else
>> + mem_cgroup_event(oc->memcg, MEMCG_OOM_KILL);
>> +
>> /* Get a reference to safely compare mm after task_unlock(victim) */
>> mm = victim->mm;
>> mmgrab(mm);
>> diff --git a/mm/vmstat.c b/mm/vmstat.c
>> index 76f73670200a..fe80b81a86e0 100644
>> --- a/mm/vmstat.c
>> +++ b/mm/vmstat.c
>> @@ -1018,6 +1018,7 @@ const char * const vmstat_text[] = {
>>
>> "drop_pagecache",
>> "drop_slab",
>> + "oom_kill",
>>
>> #ifdef CONFIG_NUMA_BALANCING
>> "numa_pte_updates",
>>
>> --
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>> see: http://www.linux-mm.org/ .
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>
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