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Thu, 12 Feb 2026 15:38:42 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id QgJZFgL0jWkaFgAAD6G6ig (envelope-from ); Thu, 12 Feb 2026 15:38:42 +0000 Message-ID: Date: Thu, 12 Feb 2026 16:38:42 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH RESEND v8] mm/page_alloc: boost watermarks on atomic allocation failure Content-Language: en-US To: Qiliang Yuan , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Axel Rasmussen , Yuanchu Xie , Wei Xu , Brendan Jackman , Johannes Weiner , Zi Yan , Lance Yang Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, kernel test robot , Qiliang Yuan References: <20260212-wujing-mm-page_alloc-v8-v8-1-daba38990cd3@gmail.com> From: Vlastimil Babka Autocrypt: addr=vbabka@suse.cz; keydata= xsFNBFZdmxYBEADsw/SiUSjB0dM+vSh95UkgcHjzEVBlby/Fg+g42O7LAEkCYXi/vvq31JTB KxRWDHX0R2tgpFDXHnzZcQywawu8eSq0LxzxFNYMvtB7sV1pxYwej2qx9B75qW2plBs+7+YB 87tMFA+u+L4Z5xAzIimfLD5EKC56kJ1CsXlM8S/LHcmdD9Ctkn3trYDNnat0eoAcfPIP2OZ+ 9oe9IF/R28zmh0ifLXyJQQz5ofdj4bPf8ecEW0rhcqHfTD8k4yK0xxt3xW+6Exqp9n9bydiy tcSAw/TahjW6yrA+6JhSBv1v2tIm+itQc073zjSX8OFL51qQVzRFr7H2UQG33lw2QrvHRXqD Ot7ViKam7v0Ho9wEWiQOOZlHItOOXFphWb2yq3nzrKe45oWoSgkxKb97MVsQ+q2SYjJRBBH4 8qKhphADYxkIP6yut/eaj9ImvRUZZRi0DTc8xfnvHGTjKbJzC2xpFcY0DQbZzuwsIZ8OPJCc LM4S7mT25NE5kUTG/TKQCk922vRdGVMoLA7dIQrgXnRXtyT61sg8PG4wcfOnuWf8577aXP1x 6mzw3/jh3F+oSBHb/GcLC7mvWreJifUL2gEdssGfXhGWBo6zLS3qhgtwjay0Jl+kza1lo+Cv BB2T79D4WGdDuVa4eOrQ02TxqGN7G0Biz5ZLRSFzQSQwLn8fbwARAQABzSBWbGFzdGltaWwg QmFia2EgPHZiYWJrYUBzdXNlLmN6PsLBlAQTAQoAPgIbAwULCQgHAwUVCgkICwUWAgMBAAIe AQIXgBYhBKlA1DSZLC6OmRA9UCJPp+fMgqZkBQJnyBr8BQka0IFQAAoJECJPp+fMgqZkqmMQ AIbGN95ptUMUvo6aAdhxaOCHXp1DfIBuIOK/zpx8ylY4pOwu3GRe4dQ8u4XS9gaZ96Gj4bC+ jwWcSmn+TjtKW3rH1dRKopvC07tSJIGGVyw7ieV/5cbFffA8NL0ILowzVg8w1ipnz1VTkWDr 2zcfslxJsJ6vhXw5/npcY0ldeC1E8f6UUoa4eyoskd70vO0wOAoGd02ZkJoox3F5ODM0kjHu Y97VLOa3GG66lh+ZEelVZEujHfKceCw9G3PMvEzyLFbXvSOigZQMdKzQ8D/OChwqig8wFBmV QCPS4yDdmZP3oeDHRjJ9jvMUKoYODiNKsl2F+xXwyRM2qoKRqFlhCn4usVd1+wmv9iLV8nPs 2Db1ZIa49fJet3Sk3PN4bV1rAPuWvtbuTBN39Q/6MgkLTYHb84HyFKw14Rqe5YorrBLbF3rl M51Dpf6Egu1yTJDHCTEwePWug4XI11FT8lK0LNnHNpbhTCYRjX73iWOnFraJNcURld1jL1nV r/LRD+/e2gNtSTPK0Qkon6HcOBZnxRoqtazTU6YQRmGlT0v+rukj/cn5sToYibWLn+RoV1CE Qj6tApOiHBkpEsCzHGu+iDQ1WT0Idtdynst738f/uCeCMkdRu4WMZjteQaqvARFwCy3P/jpK uvzMtves5HvZw33ZwOtMCgbpce00DaET4y/UzsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZ8gcVAUJFhTonwAKCRAiT6fnzIKmZLY8D/9uo3Ut9yi2YCuASWxr7QQZ lJCViArjymbxYB5NdOeC50/0gnhK4pgdHlE2MdwF6o34x7TPFGpjNFvycZqccSQPJ/gibwNA zx3q9vJT4Vw+YbiyS53iSBLXMweeVV1Jd9IjAoL+EqB0cbxoFXvnjkvP1foiiF5r73jCd4PR rD+GoX5BZ7AZmFYmuJYBm28STM2NA6LhT0X+2su16f/HtummENKcMwom0hNu3MBNPUOrujtW khQrWcJNAAsy4yMoJ2Lw51T/5X5Hc7jQ9da9fyqu+phqlVtn70qpPvgWy4HRhr25fCAEXZDp xG4RNmTm+pqorHOqhBkI7wA7P/nyPo7ZEc3L+ZkQ37u0nlOyrjbNUniPGxPxv1imVq8IyycG AN5FaFxtiELK22gvudghLJaDiRBhn8/AhXc642/Z/yIpizE2xG4KU4AXzb6C+o7LX/WmmsWP Ly6jamSg6tvrdo4/e87lUedEqCtrp2o1xpn5zongf6cQkaLZKQcBQnPmgHO5OG8+50u88D9I rywqgzTUhHFKKF6/9L/lYtrNcHU8Z6Y4Ju/MLUiNYkmtrGIMnkjKCiRqlRrZE/v5YFHbayRD dJKXobXTtCBYpLJM4ZYRpGZXne/FAtWNe4KbNJJqxMvrTOrnIatPj8NhBVI0RSJRsbilh6TE m6M14QORSWTLRg== In-Reply-To: <20260212-wujing-mm-page_alloc-v8-v8-1-daba38990cd3@gmail.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspam-User: X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 5651018000D X-Stat-Signature: 1dpu5buc7f1xpfizawrze4oi3h55tkth X-HE-Tag: 1770910724-955700 X-HE-Meta: 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 Ekeg6Ch6 Sw07Sv5LiEKQfVIDQEVaWQdF3IuFzPERvD/zdoVmjxcyVp1z5JZt9uW7YSR+BEJkjANL1RwhR9t39dsaQimDc5AEuaER12HYyd7Z1i5Njz8+sPINw7Mk9WrEoCRqB1Rs6Ih1zqOZg3X0yzwGp9As/smnzn5lqIRdkfeheaFb+4ZDyoKPb7u+/5eX44OMCxbjLQ+mlvUhSfRNbmM/gsY/46dX3rkVE6a2EJ+xqBNhJpjpXNbBJKTSUC5jJVvJWdLqMHFB9m/KbT8Y4NC3xrz/T27kZ53ETd15l+bVRZcEAxv2XGdWvKpqZ4Fms4NF3qKaqk3UoIkaG7ZlCuw1E7ivVSIVHBDMDeWJ2duY9qjgulq1tDR3ihDcIQkyKQjQKcqgaKgmFZkKgLMB7RVVuO1hFbyIH8g== 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: On 2/12/26 08:27, Qiliang Yuan wrote: > Atomic allocations (GFP_ATOMIC) are prone to failure under heavy memory > pressure as they cannot enter direct reclaim. This patch introduces a > watermark boost mechanism to mitigate this issue. > > When a GFP_ATOMIC request enters the slowpath, the preferred zone's > watermark_boost is increased under zone->lock protection. This triggers > kswapd to proactively reclaim memory, creating a safety buffer for > future atomic allocations. A 1-second debounce timer prevents excessive > boosts during traffic bursts. > > This approach reuses existing watermark_boost infrastructure with > minimal overhead and proper locking to ensure thread safety. > > 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 > > Reported-by: kernel test robot > Closes: https://lore.kernel.org/oe-lkp/202601271341.5d24a59f-lkp@intel.com > Signed-off-by: Qiliang Yuan > Signed-off-by: Qiliang Yuan Acked-by: Vlastimil Babka Nit: > --- > v8: > - Use spin_lock_irqsave() to prevent inconsistent lock state (softirq-on > vs in-softirq) as reported by LKP. > v7: > - Use local variable for boost_amount to improve code readability > - Add zone->lock protection in boost_zones_for_atomic() > - Add lockdep assertion in boost_watermark() to prevent locking mistakes > - Remove redundant boost call at fail label due to 1-second debounce > - Link: https://lore.kernel.org/all/20260123064231.250767-1-realwujing@gmail.com/ > 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 | 48 ++++++++++++++++++++++++++++++++++++++++++++++-- > 2 files changed, 47 insertions(+), 2 deletions(-) > > diff --git a/include/linux/mmzone.h b/include/linux/mmzone.h > index 75ef7c9f9307..8e37e4e6765b 100644 > --- a/include/linux/mmzone.h > +++ b/include/linux/mmzone.h > @@ -882,6 +882,7 @@ struct zone { > /* zone watermarks, access with *_wmark_pages(zone) macros */ > unsigned long _watermark[NR_WMARK]; > unsigned long watermark_boost; > + unsigned long last_boost_jiffies; > > unsigned long nr_reserved_highatomic; > unsigned long nr_free_highatomic; > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index c380f063e8b7..7dc1e056a082 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) > @@ -2161,6 +2168,9 @@ bool pageblock_unisolate_and_move_free_pages(struct zone *zone, struct page *pag > static inline bool boost_watermark(struct zone *zone) > { > unsigned long max_boost; > + unsigned long boost_amount; > + > + lockdep_assert_held(&zone->lock); > > if (!watermark_boost_factor) > return false; > @@ -2189,12 +2199,42 @@ static inline bool boost_watermark(struct zone *zone) > > max_boost = max(pageblock_nr_pages, max_boost); > > - zone->watermark_boost = min(zone->watermark_boost + pageblock_nr_pages, > - max_boost); > + boost_amount = max(pageblock_nr_pages, > + zone_managed_pages(zone) >> ATOMIC_BOOST_SCALE_SHIFT); > + zone->watermark_boost = min(zone->watermark_boost + boost_amount, > + max_boost); > > return true; > } > > +static void boost_zones_for_atomic(struct alloc_context *ac, gfp_t gfp_mask) > +{ > + struct zoneref *z; > + struct zone *zone; > + unsigned long now = jiffies; > + bool should_wake; > + > + for_each_zone_zonelist(zone, z, ac->zonelist, ac->highest_zoneidx) { > + /* Rate-limit boosts to once per second per zone */ > + if (time_after(now, zone->last_boost_jiffies + HZ)) { > + unsigned long flags; > + > + zone->last_boost_jiffies = now; > + > + /* Modify watermark under lock, wake kswapd outside */ > + spin_lock_irqsave(&zone->lock, flags); > + should_wake = boost_watermark(zone); > + spin_unlock_irqrestore(&zone->lock, flags); > + > + if (should_wake) > + wakeup_kswapd(zone, gfp_mask, 0, ac->highest_zoneidx); > + > + /* Boost only the preferred zone */ > + break; > + } > + } > +} > + > /* > * When we are falling back to another migratetype during allocation, should we > * try to claim an entire block to satisfy further allocations, instead of > @@ -4742,6 +4782,10 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, > if (page) > goto got_pg; > > + /* Boost watermarks for atomic requests entering slowpath */ > + if ((gfp_mask & GFP_ATOMIC) && order == 0) I'd also test && !can_direct_reclaim, we don't want to boost for allocations that can reclaim and yet specify __GFP_HIGH. > + boost_zones_for_atomic(ac, gfp_mask); > + > /* > * For costly allocations, try direct compaction first, as it's likely > * that we have enough base pages and don't need to reclaim. For non- > > --- > base-commit: b54345928fa1dbde534e32ecaa138678fd5d2135 > change-id: 20260206-wujing-mm-page_alloc-v8-fb1979bac6fe > > Best regards,