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Wed, 21 Jan 2026 18:00:45 -0800 (PST) Received: from debian ([74.48.213.230]) by smtp.gmail.com with ESMTPSA id 5a478bee46e88-2b6b361f5d4sm23807434eec.17.2026.01.21.18.00.40 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 21 Jan 2026 18:00:45 -0800 (PST) From: Qiliang Yuan To: akpm@linux-foundation.org Cc: david@kernel.org, mhocko@suse.com, vbabka@suse.cz, willy@infradead.org, lance.yang@linux.dev, hannes@cmpxchg.org, surenb@google.com, jackmanb@google.com, ziy@nvidia.com, weixugc@google.com, rppt@kernel.org, linux-mm@kvack.org, linux-kernel@vger.kernel.org, netdev@vger.kernel.org, edumazet@google.com, jis1@chinatelecom.cn, wangh13@chinatelecom.cn, liyi1@chinatelecom.cn, sunshx@chinatelecom.cn, zhangzq20@chinatelecom.cn, zhangjn11@chinatelecom.cn, Qiliang Yuan , Qiliang Yuan Subject: [PATCH] mm/page_alloc: boost watermarks on atomic allocation failure Date: Wed, 21 Jan 2026 21:00:35 -0500 Message-ID: <20260122020035.227449-1-realwujing@gmail.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20260121125603.47b204cc8fbe9466b25cce16@linux-foundation.org> References: <20260121125603.47b204cc8fbe9466b25cce16@linux-foundation.org> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam11 X-Stat-Signature: sf6w4gor1otagh75unbkchwqq49hbjez X-Rspam-User: X-Rspamd-Queue-Id: 8AEB62000D X-HE-Tag: 1769047247-19093 X-HE-Meta: U2FsdGVkX18rELeQjWnX4RqjMLC18sWeuUZoGQMSZ43Q1nBfmiVvC1vlV6wASXR4jl7tcZY4Pi6kqZqa0f3viawRXdZEONo0fRQQm8SdTBAPMN2igPkxidrhYP2Alovih0Z8iFfL4s3TBFdrvyLu872cVMkx9g1dLAAtzrY8dGA8BUZgYNR6Jeewaq5psgx4SIf9Ai8LejaOlynr5uxktf0q6G/uG6oN0eN6wsVMpG9X0nVBj8yug+O+GJgmBhJwzk9Le+hcnOw36oSGFxHah4og95OJAATlzy/11uqvFcFwT/mQK9viR0XA0MbDL896fOgOkNL0VQm/RyPVNehO6XPGYAo3dO71lJdCfqaHUA3xnVqAxg4sbF7ich7B0yJFvYEz+YUw9TlnWxZBoicMwBzPXXzGCbmbuTRA5WUTnofUUSmgsNmY0hm7HHbHbkY1+55a6gx0t1YxhytvjFm76gXgqUZGtGg7HygfwJU1x222ROL9M/vn59sPKHTpUp3fQ+2/geONAe95/fp6g1ytAeL+3Cwz/53jmCk+mPanCWOFoxYCxmwaaXY0hF43EfHqrbRPuqsFKYF2Erdd6ucdAw2pXoWBuVAlhKQXuwPxKCKyyGVSZBzRP3iUwCzu/AeVKwonPI7r33Fc/PCsbejGRBmXZubc7oaom2uiwxZp2oneivmhn6OEVwjNYtTaSAkBpymOX2R0b9aiidQ/6M/ahcZJ3iZl/wWaRI2F3KPpp4tVU9oQ74DtiQIoPr1cxIqyam0Lh8nwkWoZiDIa+B2bj2QAuFgrLB/kaFd85LaR5QIohSNOXL93EASqqkVbino8K2znCYx33B/FipErgDcP6yQye0aQTr729aMpFi5qUrrDkoZZkhmYNvKEWhClLoTOyixT+68YXNdq1NtyurBEc/bM8nhSxrXwW/7hcpymsLKYRRirGokDo0XSxqsU5XurbiRpeoi0TDIRvPuKHEz sc2Nkag6 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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: Atomic allocations (GFP_ATOMIC) are prone to failure under heavy memory pressure as they cannot enter direct reclaim. This patch introduces a 'Soft Boost' mechanism to mitigate this. When a GFP_ATOMIC request fails or enters the slowpath, the preferred zone's watermark_boost is increased. This triggers kswapd to proactively reclaim memory, creating a safety buffer for future atomic bursts. To prevent excessive reclaim during packet storms, a 1-second debounce timer (last_boost_jiffies) is added to each zone to rate-limit boosts. This approach reuses existing watermark_boost infrastructure, ensuring minimal overhead and asynchronous background reclaim via kswapd. Allocation failure logs: [38535644.718700] node 0: slabs: 1031, objs: 43328, free: 0 [38535644.725059] node 1: slabs: 339, objs: 17616, free: 317 [38535645.428345] SLUB: Unable to allocate memory on node -1, gfp=0x480020(GFP_ATOMIC) [38535645.436888] cache: skbuff_head_cache, object size: 232, buffer size: 256, default order: 2, min order: 0 [38535645.447664] node 0: slabs: 940, objs: 40864, free: 144 [38535645.454026] node 1: slabs: 322, objs: 19168, free: 383 [38535645.556122] SLUB: Unable to allocate memory on node -1, gfp=0x480020(GFP_ATOMIC) [38535645.564576] cache: skbuff_head_cache, object size: 232, buffer size: 256, default order: 2, min order: 0 [38535649.655523] warn_alloc: 59 callbacks suppressed [38535649.655527] swapper/100: page allocation failure: order:0, mode:0x480020(GFP_ATOMIC), nodemask=(null) [38535649.671692] swapper/100 cpuset=/ mems_allowed=0-1 Signed-off-by: Qiliang Yuan Signed-off-by: Qiliang Yuan --- v6: - Replace magic number ">> 10" with ATOMIC_BOOST_SCALE_SHIFT define - Add documentation explaining 0.1% zone size boost rationale v5: - Simplify to use native boost_watermark() instead of custom logic v4: - Add watermark_scale_boost and gradual decay via balance_pgdat v3: - Move debounce timer to per-zone; optimize zone selection v2: - Add debounce logic and zone-proportional boosting v1: - Initial: boost min_free_kbytes on GFP_ATOMIC failure --- include/linux/mmzone.h | 1 + mm/page_alloc.c | 36 +++++++++++++++++++++++++++++++++++- 2 files changed, 36 insertions(+), 1 deletion(-) --- mm/page_alloc.c | 9 ++++++++- 1 file changed, 8 insertions(+), 1 deletion(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 1faace9e2dc5..8ea2435125d5 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -218,6 +218,13 @@ unsigned int pageblock_order __read_mostly; static void __free_pages_ok(struct page *page, unsigned int order, fpi_t fpi_flags); +/* + * Boost watermarks by ~0.1% of zone size on atomic allocation pressure. + * This provides zone-proportional safety buffers: ~1MB per 1GB of zone size. + * Larger zones under GFP_ATOMIC pressure need proportionally larger reserves. + */ +#define ATOMIC_BOOST_SCALE_SHIFT 10 + /* * results with 256, 32 in the lowmem_reserve sysctl: * 1G machine -> (16M dma, 800M-16M normal, 1G-800M high) @@ -2190,7 +2197,7 @@ static inline bool boost_watermark(struct zone *zone) max_boost = max(pageblock_nr_pages, max_boost); zone->watermark_boost = min(zone->watermark_boost + - max(pageblock_nr_pages, zone_managed_pages(zone) >> 10), + max(pageblock_nr_pages, zone_managed_pages(zone) >> ATOMIC_BOOST_SCALE_SHIFT), max_boost); return true; -- 2.51.0