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Date: Mon, 19 Dec 2016 15:21:25 -0800 From: Andrew Morton <akpm@...ux-foundation.org> To: Michal Hocko <mhocko@...nel.org> Cc: Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>, <linux-mm@...ck.org>, LKML <linux-kernel@...r.kernel.org>, Michal Hocko <mhocko@...e.com> Subject: Re: [PATCH] mm: throttle show_mem from warn_alloc On Thu, 15 Dec 2016 11:15:10 +0100 Michal Hocko <mhocko@...nel.org> 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) _
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