mm: help __GFP_NOFAIL allocations which do not trigger OOM killer (6c18ba7a) · Commits · 戴 / test

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@kernel.org Signed-off-by:

Michal Hocko <mhocko@suse.com> Cc: Vlastimil Babka <vbabka@suse.cz> Cc: Johannes Weiner <hannes@cmpxchg.org> Cc: Hillf Danton <hillf.zj@alibaba-inc.com> Cc: Tetsuo Handa <penguin-kernel@I-love.SAKURA.ne.jp> Signed-off-by:

Andrew Morton <akpm@linux-foundation.org> Signed-off-by:

Linus Torvalds <torvalds@linux-foundation.org>

mm/page_alloc.c

+36 −10

Original line number	Diff line number	Diff line
		@@ -3055,6 +3055,26 @@ void warn_alloc(gfp_t gfp_mask, nodemask_t nodemask, const char fmt, ...)
		warn_alloc_show_mem(gfp_mask, nm);
		}

		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)
		@@ -3119,18 +3139,14 @@ __alloc_pages_may_oom(gfp_t gfp_mask, unsigned int order,
		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
		* Help non-failing allocations by giving them access to memory
		* reserves
		*/
		if (!page)
		page = get_page_from_freelist(gfp_mask, order,
		if (gfp_mask & __GFP_NOFAIL)
		page = __alloc_pages_cpuset_fallback(gfp_mask, order,
		ALLOC_NO_WATERMARKS, ac);
		}
		}
		out:
		mutex_unlock(&oom_lock);
		return page;
		@@ -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;
		}

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