On Wed 08-11-17 09:18:42, Dmitry Monakhov wrote:
> Our systems becomes bigger and bigger, but OOM still happens.
> This becomes serious problem for systems where OOM happens
> frequently(containers, VM) because each OOM generate pressure
> on dmesg log infrastructure. Let's allow system administrator
> ability to tune OOM dump behaviour
>
> Disable oom log dump globaly:
> # echo 0 > /proc/sys/vm/oom_dump_log
> Enable oom log dump globaly:
> # echo 1 > /proc/sys/vm/oom_dump_log
We already do have sysctl_oom_dump_tasks to silence a potentially
lengthy task list output. show_mem is using a default print level
but I can imagine we can make it pr_info. Would that be sufficient?
I have to confess I am not really happy yet another tunable to control
the output. The same applies to the memcg case in the other email.
> Signed-off-by: Dmitry Monakhov <dmonakhov@xxxxxxxxxx>
> ---
> Documentation/sysctl/vm.txt | 13 +++++++++++++
> include/linux/oom.h | 1 +
> kernel/sysctl.c | 7 +++++++
> mm/oom_kill.c | 40 ++++++++++++++++++++++------------------
> 4 files changed, 43 insertions(+), 18 deletions(-)
>
> diff --git a/Documentation/sysctl/vm.txt b/Documentation/sysctl/vm.txt
> index 9baf66a..09d69a0 100644
> --- a/Documentation/sysctl/vm.txt
> +++ b/Documentation/sysctl/vm.txt
> @@ -617,7 +617,20 @@ Default order is recommended unless this is causing problems for your
> system/application.
>
> ==============================================================
> +oom_dump_log
>
> +Enables a system-wide dump to be produced when the kernel performs an
> +OOM-killing. This sysctl control dump about general information of OOM state
> +
> +If this is set to zero, this information is suppressed. On very
> +large systems with thousands of tasks it may not be feasible to dump
> +the memory state information for each OOM event. Such systems should
> +not be forced to incur a performance penalty in OOM conditions when the
> +information may not be desired.
> +
> +The default value is 1 (enabled).
> +
> +==============================================================
> oom_dump_tasks
>
> Enables a system-wide task dump (excluding kernel threads) to be produced
> diff --git a/include/linux/oom.h b/include/linux/oom.h
> index 01c91d8..8ff56d3 100644
> --- a/include/linux/oom.h
> +++ b/include/linux/oom.h
> @@ -104,6 +104,7 @@ extern unsigned long oom_badness(struct task_struct *p,
>
> /* sysctls */
> extern int sysctl_oom_dump_tasks;
> +extern int sysctl_oom_dump_log;
> extern int sysctl_oom_kill_allocating_task;
> extern int sysctl_panic_on_oom;
> #endif /* _INCLUDE_LINUX_OOM_H */
> diff --git a/kernel/sysctl.c b/kernel/sysctl.c
> index d9c31bc..87163c1 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -1263,6 +1263,13 @@ static int sysrq_sysctl_handler(struct ctl_table *table, int write,
> .proc_handler = proc_dointvec,
> },
> {
> + .procname = "oom_dump_log",
> + .data = &sysctl_oom_dump_log,
> + .maxlen = sizeof(sysctl_oom_dump_log),
> + .mode = 0644,
> + .proc_handler = proc_dointvec,
> + },
> + {
> .procname = "overcommit_ratio",
> .data = &sysctl_overcommit_ratio,
> .maxlen = sizeof(sysctl_overcommit_ratio),
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index dee0f75..02c8f5d6 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -51,6 +51,7 @@
> int sysctl_panic_on_oom;
> int sysctl_oom_kill_allocating_task;
> int sysctl_oom_dump_tasks = 1;
> +int sysctl_oom_dump_log = 1;
>
> DEFINE_MUTEX(oom_lock);
>
> @@ -552,7 +553,8 @@ static bool __oom_reap_task_mm(struct task_struct *tsk, struct mm_struct *mm)
> NULL);
> }
> tlb_finish_mmu(&tlb, 0, -1);
> - pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
> + if (sysctl_oom_dump_log)
> + pr_info("oom_reaper: reaped process %d (%s), now anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
> task_pid_nr(tsk), tsk->comm,
> K(get_mm_counter(mm, MM_ANONPAGES)),
> K(get_mm_counter(mm, MM_FILEPAGES)),
> @@ -578,11 +580,11 @@ static void oom_reap_task(struct task_struct *tsk)
> if (attempts <= MAX_OOM_REAP_RETRIES)
> goto done;
>
> -
> - pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
> - task_pid_nr(tsk), tsk->comm);
> - debug_show_all_locks();
> -
> + if (sysctl_oom_dump_log) {
> + pr_info("oom_reaper: unable to reap pid:%d (%s)\n",
> + task_pid_nr(tsk), tsk->comm);
> + debug_show_all_locks();
> + }
> done:
> tsk->oom_reaper_list = NULL;
>
> @@ -647,7 +649,7 @@ static int __init oom_init(void)
> }
> subsys_initcall(oom_init)
> #else
> -static inline void wake_oom_reaper(struct task_struct *tsk)
> +static inline void wake_oom_reaper(struct task_struct *tsk, bool verbose)
> {
> }
> #endif /* CONFIG_MMU */
> @@ -847,13 +849,13 @@ static void oom_kill_process(struct oom_control *oc, const char *message)
> return;
> }
> task_unlock(p);
> + if (sysctl_oom_dump_log) {
> + if (__ratelimit(&oom_rs))
> + dump_header(oc, p);
>
> - if (__ratelimit(&oom_rs))
> - dump_header(oc, p);
> -
> - pr_err("%s: Kill process %d (%s) score %u or sacrifice child\n",
> - message, task_pid_nr(p), p->comm, points);
> -
> + pr_err("%s: Kill process %d (%s) score %u or sacrifice child\n",
> + message, task_pid_nr(p), p->comm, points);
> + }
> /*
> * If any of p's children has a different mm and is eligible for kill,
> * the one with the highest oom_badness() score is sacrificed for its
> @@ -907,11 +909,13 @@ static void oom_kill_process(struct oom_control *oc, const char *message)
> */
> do_send_sig_info(SIGKILL, SEND_SIG_FORCED, victim, true);
> mark_oom_victim(victim);
> - pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
> - task_pid_nr(victim), victim->comm, K(victim->mm->total_vm),
> - K(get_mm_counter(victim->mm, MM_ANONPAGES)),
> - K(get_mm_counter(victim->mm, MM_FILEPAGES)),
> - K(get_mm_counter(victim->mm, MM_SHMEMPAGES)));
> + if (sysctl_oom_dump_log)
> + pr_err("Killed process %d (%s) total-vm:%lukB, anon-rss:%lukB, file-rss:%lukB, shmem-rss:%lukB\n",
> + task_pid_nr(victim), victim->comm,
> + K(victim->mm->total_vm),
> + K(get_mm_counter(victim->mm, MM_ANONPAGES)),
> + K(get_mm_counter(victim->mm, MM_FILEPAGES)),
> + K(get_mm_counter(victim->mm, MM_SHMEMPAGES)));
> task_unlock(victim);
>
> /*
> --
> 1.8.3.1
>
> --
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--
Michal Hocko
SUSE Labs
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