On Mon 19-12-16 15:21:25, Andrew Morton wrote: > On Thu, 15 Dec 2016 11:15:10 +0100 Michal Hocko <[email protected]> wrote: > > > Tetsuo has been stressing OOM killer path with many parallel allocation > > requests when he has noticed that it is not all that hard to swamp > > kernel logs with warn_alloc messages caused by allocation stalls. Even > > though the allocation stall message is triggered only once in 10s there > > might be many different tasks hitting it roughly around the same time. > > > > A big part of the output is show_mem() which can generate a lot of > > output even on a small machines. There is no reason to show the state of > > memory counter for each allocation stall, especially when multiple of > > them are reported in a short time period. Chances are that not much has > > changed since the last report. This patch simply rate limits show_mem > > called from warn_alloc to only dump something once per second. This > > should be enough to give us a clue why an allocation might be stalling > > while burst of warnings will not swamp log with too much data. > > > > While we are at it, extract all the show_mem related handling (filters) > > into a separate function warn_alloc_show_mem. This will make the code > > cleaner and as a bonus point we can distinguish which part of warn_alloc > > got throttled due to rate limiting as ___ratelimit dumps the caller. > > These guys don't need file-wide scope... > > --- a/mm/page_alloc.c~mm-throttle-show_mem-from-warn_alloc-fix > +++ a/mm/page_alloc.c > @@ -3018,15 +3018,10 @@ static inline bool should_suppress_show_ > return ret; > } > > -static DEFINE_RATELIMIT_STATE(nopage_rs, > - DEFAULT_RATELIMIT_INTERVAL, > - DEFAULT_RATELIMIT_BURST); > - > -static DEFINE_RATELIMIT_STATE(show_mem_rs, HZ, 1); > - > static void warn_alloc_show_mem(gfp_t gfp_mask) > { > unsigned int filter = SHOW_MEM_FILTER_NODES; > + static DEFINE_RATELIMIT_STATE(show_mem_rs, HZ, 1); > > if (should_suppress_show_mem() || !__ratelimit(&show_mem_rs)) > return; > @@ -3050,6 +3045,8 @@ void warn_alloc(gfp_t gfp_mask, const ch > { > struct va_format vaf; > va_list args; > + static DEFINE_RATELIMIT_STATE(nopage_rs, DEFAULT_RATELIMIT_INTERVAL, > + DEFAULT_RATELIMIT_BURST); > > if ((gfp_mask & __GFP_NOWARN) || !__ratelimit(&nopage_rs) || > debug_guardpage_minorder() > 0) > _ >
Acked-by: Michal Hocko <[email protected]> -- Michal Hocko SUSE Labs
