On Fri, 23 Oct 2015 17:02:30 -0400 Aristeu Rozanski <arozansk@xxxxxxxxxx> wrote:
> One of the largest chunks of log messages in a OOM is from dump_stack() and in
> some cases it isn't even necessary to figure out what's going on. In
> systems with multiple tenants/containers with limited resources each
> OOMs can be way more frequent and being able to reduce the amount of log
> output for each situation is useful.
>
> This patch adds a sysctl to allow disabling dump_stack() during an OOM while
> keeping the default to behave the same way it behaves today.
Can you get the same effect by using "dmesg -n <N>"? Probably not, I
didn't look.
> --- a/include/linux/oom.h
> +++ b/include/linux/oom.h
> @@ -115,6 +115,7 @@ static inline bool task_will_free_mem(struct task_struct *task)
>
> /* sysctls */
> extern int sysctl_oom_dump_tasks;
> +extern int sysctl_oom_dump_stack;
> 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 e69201d..c812523 100644
> --- a/kernel/sysctl.c
> +++ b/kernel/sysctl.c
> @@ -1176,6 +1176,13 @@ static struct ctl_table vm_table[] = {
> .proc_handler = proc_dointvec,
> },
> {
> + .procname = "oom_dump_stack",
> + .data = &sysctl_oom_dump_stack,
> + .maxlen = sizeof(sysctl_oom_dump_stack),
> + .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 1ecc0bc..bdbf83b 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -42,6 +42,7 @@
> int sysctl_panic_on_oom;
> int sysctl_oom_kill_allocating_task;
> int sysctl_oom_dump_tasks = 1;
> +int sysctl_oom_dump_stack = 1;
>
> DEFINE_MUTEX(oom_lock);
>
> @@ -384,7 +385,8 @@ static void dump_header(struct oom_control *oc, struct task_struct *p,
> current->signal->oom_score_adj);
> cpuset_print_task_mems_allowed(current);
> task_unlock(current);
> - dump_stack();
> + if (sysctl_oom_dump_stack)
> + dump_stack();
> if (memcg)
> mem_cgroup_print_oom_info(memcg, p);
> else
The patch seems reasonable to me, but it's missing the required update
to Documentation/sysctl/vm.txt.
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