From: Michal Hocko <mhocko@xxxxxxxx> Subject: mm: warn about allocations which stall for too long Currently we do warn only about allocation failures but small allocations are basically nofail and they might loop in the page allocator for a long time. Especially when the reclaim cannot make any progress - e.g. GFP_NOFS cannot invoke the oom killer and rely on a different context to make a forward progress in case there is a lot memory used by filesystems. Give us at least a clue when something like this happens and warn about allocations which take more than 10s. Print the basic allocation context information along with the cumulative time spent in the allocation as well as the allocation stack. Repeat the warning after every 10 seconds so that we know that the problem is permanent rather than ephemeral. Link: http://lkml.kernel.org/r/20160929084407.7004-3-mhocko@xxxxxxxxxx Signed-off-by: Michal Hocko <mhocko@xxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Mel Gorman <mgorman@xxxxxxx> Cc: Dave Hansen <dave.hansen@xxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/page_alloc.c | 10 ++++++++++ 1 file changed, 10 insertions(+) diff -puN mm/page_alloc.c~mm-warn-about-allocations-which-stall-for-too-long mm/page_alloc.c --- a/mm/page_alloc.c~mm-warn-about-allocations-which-stall-for-too-long +++ a/mm/page_alloc.c @@ -3493,6 +3493,8 @@ __alloc_pages_slowpath(gfp_t gfp_mask, u enum compact_result compact_result; int compaction_retries = 0; int no_progress_loops = 0; + unsigned long alloc_start = jiffies; + unsigned int stall_timeout = 10 * HZ; /* * In the slowpath, we sanity check order to avoid ever trying to @@ -3648,6 +3650,14 @@ retry: if (order > PAGE_ALLOC_COSTLY_ORDER && !(gfp_mask & __GFP_REPEAT)) goto nopage; + /* Make sure we know about allocations which stall for too long */ + if (time_after(jiffies, alloc_start + stall_timeout)) { + warn_alloc(gfp_mask, + "page alloction stalls for %ums, order:%u\n", + jiffies_to_msecs(jiffies-alloc_start), order); + stall_timeout += 10 * HZ; + } + if (should_reclaim_retry(gfp_mask, order, ac, alloc_flags, did_some_progress > 0, &no_progress_loops)) goto retry; _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
