From: Michal Hocko <mhocko@xxxxxxxx> Subject: mm: help __GFP_NOFAIL allocations which do not trigger OOM killer Now that __GFP_NOFAIL doesn't override decisions to skip the oom killer we are left with requests which require to loop inside the allocator without invoking the oom killer (e.g. GFP_NOFS|__GFP_NOFAIL used by fs code) and so they might, in very unlikely situations, loop for ever - e.g. other parallel request could starve them. This patch tries to limit the likelihood of such a lockup by giving these __GFP_NOFAIL requests a chance to move on by consuming a small part of memory reserves. We are using ALLOC_HARDER which should be enough to prevent from the starvation by regular allocation requests, yet it shouldn't consume enough from the reserves to disrupt high priority requests (ALLOC_HIGH). While we are at it, let's introduce a helper __alloc_pages_cpuset_fallback which enforces the cpusets but allows to fallback to ignore them if the first attempt fails. __GFP_NOFAIL requests can be considered important enough to allow cpuset runaway in order for the system to move on. It is highly unlikely that any of these will be GFP_USER anyway. Link: http://lkml.kernel.org/r/20161220134904.21023-4-mhocko@xxxxxxxxxx Signed-off-by: Michal Hocko <mhocko@xxxxxxxx> Cc: Vlastimil Babka <vbabka@xxxxxxx> Cc: Johannes Weiner <hannes@xxxxxxxxxxx> Cc: Hillf Danton <hillf.zj@xxxxxxxxxxxxxxx> Cc: Tetsuo Handa <penguin-kernel@xxxxxxxxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- mm/page_alloc.c | 46 ++++++++++++++++++++++++++++++++++++---------- 1 file changed, 36 insertions(+), 10 deletions(-) diff -puN mm/page_alloc.c~mm-help-__gfp_nofail-allocations-which-do-not-trigger-oom-killer mm/page_alloc.c --- a/mm/page_alloc.c~mm-help-__gfp_nofail-allocations-which-do-not-trigger-oom-killer +++ a/mm/page_alloc.c @@ -3056,6 +3056,26 @@ void warn_alloc(gfp_t gfp_mask, nodemask } static inline struct page * +__alloc_pages_cpuset_fallback(gfp_t gfp_mask, unsigned int order, + unsigned int alloc_flags, + const struct alloc_context *ac) +{ + struct page *page; + + page = get_page_from_freelist(gfp_mask, order, + alloc_flags|ALLOC_CPUSET, ac); + /* + * fallback to ignore cpuset restriction if our nodes + * are depleted + */ + if (!page) + page = get_page_from_freelist(gfp_mask, order, + alloc_flags, ac); + + return page; +} + +static inline struct page * __alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order, const struct alloc_context *ac, unsigned long *did_some_progress) { @@ -3119,17 +3139,13 @@ __alloc_pages_may_oom(gfp_t gfp_mask, un if (out_of_memory(&oc) || WARN_ON_ONCE(gfp_mask & __GFP_NOFAIL)) { *did_some_progress = 1; - if (gfp_mask & __GFP_NOFAIL) { - page = get_page_from_freelist(gfp_mask, order, - ALLOC_NO_WATERMARKS|ALLOC_CPUSET, ac); - /* - * fallback to ignore cpuset restriction if our nodes - * are depleted - */ - if (!page) - page = get_page_from_freelist(gfp_mask, order, + /* + * Help non-failing allocations by giving them access to memory + * reserves + */ + if (gfp_mask & __GFP_NOFAIL) + page = __alloc_pages_cpuset_fallback(gfp_mask, order, ALLOC_NO_WATERMARKS, ac); - } } out: mutex_unlock(&oom_lock); @@ -3785,6 +3801,16 @@ nopage: */ WARN_ON_ONCE(order > PAGE_ALLOC_COSTLY_ORDER); + /* + * Help non-failing allocations by giving them access to memory + * reserves but do not use ALLOC_NO_WATERMARKS because this + * could deplete whole memory reserves which would just make + * the situation worse + */ + page = __alloc_pages_cpuset_fallback(gfp_mask, order, ALLOC_HARDER, ac); + if (page) + goto got_pg; + cond_resched(); 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
