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Mon, 28 Oct 2024 18:33:45 +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 QRMqFwnZH2ePSAAAD6G6ig (envelope-from ); Mon, 28 Oct 2024 18:33:45 +0000 Message-ID: Date: Mon, 28 Oct 2024 19:33:45 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH mm-unstable v3] mm/page_alloc: keep track of free highatomic Content-Language: en-US To: Yu Zhao , Andrew Morton Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org, Link Lin , David Rientjes References: <20241028182653.3420139-1-yuzhao@google.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+fMgqZkBQJkBREIBQkRadznAAoJECJPp+fMgqZkNxIQ ALZRqwdUGzqL2aeSavbum/VF/+td+nZfuH0xeWiO2w8mG0+nPd5j9ujYeHcUP1edE7uQrjOC Gs9sm8+W1xYnbClMJTsXiAV88D2btFUdU1mCXURAL9wWZ8Jsmz5ZH2V6AUszvNezsS/VIT87 AmTtj31TLDGwdxaZTSYLwAOOOtyqafOEq+gJB30RxTRE3h3G1zpO7OM9K6ysLdAlwAGYWgJJ V4JqGsQ/lyEtxxFpUCjb5Pztp7cQxhlkil0oBYHkudiG8j1U3DG8iC6rnB4yJaLphKx57NuQ PIY0Bccg+r9gIQ4XeSK2PQhdXdy3UWBr913ZQ9AI2usid3s5vabo4iBvpJNFLgUmxFnr73SJ KsRh/2OBsg1XXF/wRQGBO9vRuJUAbnaIVcmGOUogdBVS9Sun/Sy4GNA++KtFZK95U7J417/J Hub2xV6Ehc7UGW6fIvIQmzJ3zaTEfuriU1P8ayfddrAgZb25JnOW7L1zdYL8rXiezOyYZ8Fm ZyXjzWdO0RpxcUEp6GsJr11Bc4F3aae9OZtwtLL/jxc7y6pUugB00PodgnQ6CMcfR/HjXlae h2VS3zl9+tQWHu6s1R58t5BuMS2FNA58wU/IazImc/ZQA+slDBfhRDGYlExjg19UXWe/gMcl De3P1kxYPgZdGE2eZpRLIbt+rYnqQKy8UxlszsBNBFsZNTUBCACfQfpSsWJZyi+SHoRdVyX5 J6rI7okc4+b571a7RXD5UhS9dlVRVVAtrU9ANSLqPTQKGVxHrqD39XSw8hxK61pw8p90pg4G /N3iuWEvyt+t0SxDDkClnGsDyRhlUyEWYFEoBrrCizbmahOUwqkJbNMfzj5Y7n7OIJOxNRkB IBOjPdF26dMP69BwePQao1M8Acrrex9sAHYjQGyVmReRjVEtv9iG4DoTsnIR3amKVk6si4Ea X/mrapJqSCcBUVYUFH8M7bsm4CSxier5ofy8jTEa/CfvkqpKThTMCQPNZKY7hke5qEq1CBk2 wxhX48ZrJEFf1v3NuV3OimgsF2odzieNABEBAAHCwXwEGAEKACYCGwwWIQSpQNQ0mSwujpkQ PVAiT6fnzIKmZAUCZAUSmwUJDK5EZgAKCRAiT6fnzIKmZOJGEACOKABgo9wJXsbWhGWYO7mD 8R8mUyJHqbvaz+yTLnvRwfe/VwafFfDMx5GYVYzMY9TWpA8psFTKTUIIQmx2scYsRBUwm5VI EurRWKqENcDRjyo+ol59j0FViYysjQQeobXBDDE31t5SBg++veI6tXfpco/UiKEsDswL1WAr tEAZaruo7254TyH+gydURl2wJuzo/aZ7Y7PpqaODbYv727Dvm5eX64HCyyAH0s6sOCyGF5/p eIhrOn24oBf67KtdAN3H9JoFNUVTYJc1VJU3R1JtVdgwEdr+NEciEfYl0O19VpLE/PZxP4wX PWnhf5WjdoNI1Xec+RcJ5p/pSel0jnvBX8L2cmniYnmI883NhtGZsEWj++wyKiS4NranDFlA HdDM3b4lUth1pTtABKQ1YuTvehj7EfoWD3bv9kuGZGPrAeFNiHPdOT7DaXKeHpW9homgtBxj 8aX/UkSvEGJKUEbFL9cVa5tzyialGkSiZJNkWgeHe+jEcfRT6pJZOJidSCdzvJpbdJmm+eED w9XOLH1IIWh7RURU7G1iOfEfmImFeC3cbbS73LQEFGe1urxvIH5K/7vX+FkNcr9ujwWuPE9b 1C2o4i/yZPLXIVy387EjA6GZMqvQUFuSTs/GeBcv0NjIQi8867H3uLjz+mQy63fAitsDwLmR EP+ylKVEKb0Q2A== In-Reply-To: <20241028182653.3420139-1-yuzhao@google.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspamd-Server: rspam06 X-Rspamd-Queue-Id: 5856E1C000F X-Stat-Signature: 5r47wmqwiodwy8exfwxxzxx9o9myysmz X-Rspam-User: X-HE-Tag: 1730140383-536303 X-HE-Meta: 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 3hayghtP q9YHTXTyiq1SEyrBi7cRr4bentgEKDf3cYfG2Jk+prFphZIBYjbu3BZ5xA0hTLd23P7F+QrF/pOPrr4ffmO+1Y+Mj/XMCrFxypyV61G2PGkFGIFa9n+hFPbX+KYxz3X462FM6MoQGKOEJP25TPkOmCap4s0ZUPDY0Gs+b7HQ1+uxUWWsaTnE6LAyfHpsV7nIhMwBxhoBh1uSciSFEW+NL0X6AqndgIENWIVb9vINzECKLwzUU3oyWhYYzC10frGC5H1D/xx+Sx99YXtsHE70wJ/AvXmaWQqhWoTCeb2+JRkA4GxAX6ixFDgxcd3o56qzpnLOVPIHDoS8tGybXfQ30OkVwgHPonqKRoCfwLp3bLG9LFaIWrvKLBYnhM+RKun0DIuGl 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 10/28/24 19:26, Yu Zhao wrote: > 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 Acked-by: Vlastimil Babka For LTS benefit I'd also add: Cc: # v6.12+ > --- > 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 */