On Thu 18-10-18 19:37:18, Tetsuo Handa wrote:
> On 2018/10/18 15:55, Michal Hocko wrote:
> > On Thu 18-10-18 11:46:50, Tetsuo Handa wrote:
> >> This is essentially a ratelimit approach, roughly equivalent with:
> >>
> >> static DEFINE_RATELIMIT_STATE(oom_no_victim_rs, 60 * HZ, 1);
> >> oom_no_victim_rs.flags |= RATELIMIT_MSG_ON_RELEASE;
> >>
> >> if (__ratelimit(&oom_no_victim_rs)) {
> >> dump_header(oc, NULL);
> >> pr_warn("Out of memory and no killable processes...\n");
> >> oom_no_victim_rs.begin = jiffies;
> >> }
> >
> > Then there is no reason to reinvent the wheel. So use the standard
> > ratelimit approach. Or put it in other words, this place is no special
> > to any other that needs some sort of printk throttling. We surely do not
> > want an ad-hoc solutions all over the kernel.
>
> netdev_wait_allrefs() in net/core/dev.c is doing the same thing. Since
> out_of_memory() is serialized by oom_lock mutex, there is no need to use
> "struct ratelimit_state"->lock field. Plain "unsigned long" is enough.
That code probably predates generalized ratelimit api.
> > And once you realize that the ratelimit api is the proper one (put aside
> > any potential improvements in the implementation of this api) then you
> > quickly learn that we already do throttle oom reports and it would be
> > nice to unify that and ... we are back to a naked patch. So please stop
> > being stuborn and try to cooperate finally.
>
> I don't think that ratelimit API is the proper one, for I am touching
> "struct ratelimit_state"->begin field which is not exported by ratelimit API.
> But if you insist on ratelimit API version, I can tolerate with below one.
I just give up. I do not really see why you always have to make the code
more complex than necessary and squash different things together. This
is a complete kernel code development antipattern.
I am not goging to reply to this thread more but let me note that this
is beyond fun in any aspect I can think off (and yeah I have considered
dark sense of humor as well).
>
> mm/oom_kill.c | 7 +++++++
> 1 file changed, 7 insertions(+)
>
> diff --git a/mm/oom_kill.c b/mm/oom_kill.c
> index f10aa53..7c6118e 100644
> --- a/mm/oom_kill.c
> +++ b/mm/oom_kill.c
> @@ -1106,6 +1106,12 @@ bool out_of_memory(struct oom_control *oc)
> select_bad_process(oc);
> /* Found nothing?!?! */
> if (!oc->chosen) {
> + static DEFINE_RATELIMIT_STATE(no_eligible_rs, 60 * HZ, 1);
> +
> + ratelimit_set_flags(&no_eligible_rs, RATELIMIT_MSG_ON_RELEASE);
> + if ((is_sysrq_oom(oc) || is_memcg_oom(oc)) &&
> + !__ratelimit(&no_eligible_rs))
> + return false;
> dump_header(oc, NULL);
> pr_warn("Out of memory and no killable processes...\n");
> /*
> @@ -1115,6 +1121,7 @@ bool out_of_memory(struct oom_control *oc)
> */
> if (!is_sysrq_oom(oc) && !is_memcg_oom(oc))
> panic("System is deadlocked on memory\n");
> + no_eligible_rs.begin = jiffies;
> }
> if (oc->chosen && oc->chosen != (void *)-1UL)
> oom_kill_process(oc, !is_memcg_oom(oc) ? "Out of memory" :
> --
> 1.8.3.1
--
Michal Hocko
SUSE Labs
