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AJvYcCVPV7uB4BwDORpX8yCbL7juhLo6Zm9NkcfMc/VZ2ZSW2o0duHexHzZVk43+Aawpxm0TNzOuMdTEJw==@kvack.org X-Gm-Message-State: AOJu0Yx8gG3k0aAUjiJs6geUM3l0lQkAQWEReXux4atWHroYHOQrgOcE IhjUQ1n1E7SNkr2CVPyGFm1t9de5hb2v4xOGbGbp75aBF5/lnkyyrqwtH92dfqvVsWLooLozmgk ZdA== X-Google-Smtp-Source: AGHT+IF9DI9pp2VPfLEJ3zKqqGeHwod+kO2SFViH2kiVn5KE0GbX5j8j/rSkrE/wdW7Vn+59QAK4wt9Kcgs= X-Received: from yuzhao2.bld.corp.google.com ([2a00:79e0:2e28:6:28ef:e08b:2af:6fd]) (user=yuzhao job=sendgmr) by 2002:a25:8512:0:b0:e2e:3401:ea0f with SMTP id 3f1490d57ef6-e3087bd5448mr92425276.7.1730140019385; Mon, 28 Oct 2024 11:26:59 -0700 (PDT) Date: Mon, 28 Oct 2024 12:26:53 -0600 Mime-Version: 1.0 X-Mailer: git-send-email 2.47.0.163.g1226f6d8fa-goog Message-ID: <20241028182653.3420139-1-yuzhao@google.com> Subject: [PATCH mm-unstable v3] mm/page_alloc: keep track of free highatomic From: Yu Zhao To: Andrew Morton Cc: Vlastimil Babka , linux-mm@kvack.org, linux-kernel@vger.kernel.org, Yu Zhao , Link Lin , David Rientjes Content-Type: text/plain; charset="UTF-8" X-Rspamd-Server: rspam07 X-Rspamd-Queue-Id: 9192740006 X-Stat-Signature: 8587c8g61wkb8sjp35x5osbpixdnnbw5 X-Rspam-User: X-HE-Tag: 1730139987-457895 X-HE-Meta: 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 ziZqlHf6 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 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: OOM kills due to vastly overestimated free highatomic reserves were observed: ... invoked oom-killer: gfp_mask=0x100cca(GFP_HIGHUSER_MOVABLE), order=0 ... Node 0 Normal free:1482936kB boost:0kB min:410416kB low:739404kB high:1068392kB reserved_highatomic:1073152KB ... Node 0 Normal: 1292*4kB (ME) 1920*8kB (E) 383*16kB (UE) 220*32kB (ME) 340*64kB (E) 2155*128kB (UE) 3243*256kB (UE) 615*512kB (U) 1*1024kB (M) 0*2048kB 0*4096kB = 1477408kB The second line above shows that the OOM kill was due to the following condition: free (1482936kB) - reserved_highatomic (1073152kB) = 409784KB < min (410416kB) And the third line shows there were no free pages in any MIGRATE_HIGHATOMIC pageblocks, which otherwise would show up as type 'H'. Therefore __zone_watermark_unusable_free() underestimated the usable free memory by over 1GB, which resulted in the unnecessary OOM kill above. The comments in __zone_watermark_unusable_free() warns about the potential risk, i.e., If the caller does not have rights to reserves below the min watermark then subtract the high-atomic reserves. This will over-estimate the size of the atomic reserve but it avoids a search. However, it is possible to keep track of free pages in reserved highatomic pageblocks with a new per-zone counter nr_free_highatomic protected by the zone lock, to avoid a search when calculating the usable free memory. And the cost would be minimal, i.e., simple arithmetics in the highatomic alloc/free/move paths. Note that since nr_free_highatomic can be relatively small, using a per-cpu counter might cause too much drift and defeat its purpose, in addition to the extra memory overhead. Reported-by: Link Lin Signed-off-by: Yu Zhao Acked-by: David Rientjes --- include/linux/mmzone.h | 1 + mm/page_alloc.c | 10 +++++++--- 2 files changed, 8 insertions(+), 3 deletions(-) diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h index 2e8c4307c728..5e8f567753bd 100644 --- a/include/linux/mmzone.h +++ b/include/linux/mmzone.h @@ -825,6 +825,7 @@ struct zone { unsigned long watermark_boost; unsigned long nr_reserved_highatomic; + unsigned long nr_free_highatomic; /* * We don't know if the memory that we're going to allocate will be diff --git a/mm/page_alloc.c b/mm/page_alloc.c index a78acaae6d9c..372a386f34f5 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -635,6 +635,8 @@ compaction_capture(struct capture_control *capc, struct page *page, static inline void account_freepages(struct zone *zone, int nr_pages, int migratetype) { + lockdep_assert_held(&zone->lock); + if (is_migrate_isolate(migratetype)) return; @@ -642,6 +644,9 @@ static inline void account_freepages(struct zone *zone, int nr_pages, if (is_migrate_cma(migratetype)) __mod_zone_page_state(zone, NR_FREE_CMA_PAGES, nr_pages); + + if (is_migrate_highatomic(migratetype)) + WRITE_ONCE(zone->nr_free_highatomic, zone->nr_free_highatomic + nr_pages); } /* Used for pages not on another list */ @@ -3117,11 +3122,10 @@ static inline long __zone_watermark_unusable_free(struct zone *z, /* * If the caller does not have rights to reserves below the min - * watermark then subtract the high-atomic reserves. This will - * over-estimate the size of the atomic reserve but it avoids a search. + * watermark then subtract the free pages reserved for highatomic. */ if (likely(!(alloc_flags & ALLOC_RESERVES))) - unusable_free += z->nr_reserved_highatomic; + unusable_free += READ_ONCE(z->nr_free_highatomic); #ifdef CONFIG_CMA /* If allocation can't use CMA areas don't use free CMA pages */ -- 2.47.0.163.g1226f6d8fa-goog