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Mon, 14 Oct 2024 10:37:45 +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 NDhDB3n0DGdlHgAAD6G6ig (envelope-from ); Mon, 14 Oct 2024 10:37:45 +0000 Message-ID: <0f46ff18-e385-4940-b0f0-db4130704bfb@suse.cz> Date: Mon, 14 Oct 2024 12:37:44 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/page_alloc: Let GFP_ATOMIC order-0 allocs access highatomic reserves Content-Language: en-US To: Matt Fleming Cc: linux-kernel@vger.kernel.org, kernel-team@cloudflare.com, Matt Fleming , Andrew Morton , Mel Gorman , linux-mm@kvack.org, Joonsoo Kim References: <20241011120737.3300370-1-matt@readmodwrite.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: <20241011120737.3300370-1-matt@readmodwrite.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspam-User: X-Stat-Signature: xkqza4zsk47zcy7gxbrzo9wsttxfqfgc X-Rspamd-Queue-Id: 23BAFA0002 X-Rspamd-Server: rspam02 X-HE-Tag: 1728902260-28236 X-HE-Meta: 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 pio7nRuh 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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: On 10/11/24 14:07, Matt Fleming wrote: > From: Matt Fleming > > Under memory pressure it's possible for GFP_ATOMIC order-0 allocations > to fail even though free pages are available in the highatomic reserves. > GFP_ATOMIC allocations cannot trigger unreserve_highatomic_pageblock() > since it's only run from reclaim. > > Given that such allocations will pass the watermarks in > __zone_watermark_unusable_free(), it makes sense to fallback to > highatomic reserves the same way that ALLOC_OOM can. > > This fixes order-0 page allocation failures observed on Cloudflare's > fleet when handling network packets: > > kswapd1: page allocation failure: order:0, mode:0x820(GFP_ATOMIC), > nodemask=(null),cpuset=/,mems_allowed=0-7 > CPU: 10 PID: 696 Comm: kswapd1 Kdump: loaded Tainted: G O 6.6.43-CUSTOM #1 > Hardware name: MACHINE > Call Trace: > > dump_stack_lvl+0x3c/0x50 > warn_alloc+0x13a/0x1c0 > __alloc_pages_slowpath.constprop.0+0xc9d/0xd10 > __alloc_pages+0x327/0x340 > __napi_alloc_skb+0x16d/0x1f0 > bnxt_rx_page_skb+0x96/0x1b0 [bnxt_en] > bnxt_rx_pkt+0x201/0x15e0 [bnxt_en] > __bnxt_poll_work+0x156/0x2b0 [bnxt_en] > bnxt_poll+0xd9/0x1c0 [bnxt_en] > __napi_poll+0x2b/0x1b0 > bpf_trampoline_6442524138+0x7d/0x1000 > __napi_poll+0x5/0x1b0 > net_rx_action+0x342/0x740 > handle_softirqs+0xcf/0x2b0 > irq_exit_rcu+0x6c/0x90 > sysvec_apic_timer_interrupt+0x72/0x90 > > > Suggested-by: Vlastimil Babka > Cc: Andrew Morton > Cc: Mel Gorman > Cc: linux-mm@kvack.org > Link: https://lore.kernel.org/all/CAGis_TWzSu=P7QJmjD58WWiu3zjMTVKSzdOwWE8ORaGytzWJwQ@mail.gmail.com/ > Signed-off-by: Matt Fleming Reviewed-by: Vlastimil Babka (but a comment should be updated, see below) I think we could add Cc: stable and I believe the commit that broke it was: Fixes: 1d91df85f399 ("mm/page_alloc: handle a missing case for memalloc_nocma_{save/restore} APIs") because it was where an order > 0 condition was introduced to allow allocation from MIGRATE_HIGHATOMIC commit eb2e2b425c69 ("mm/page_alloc: explicitly record high-order atomic allocations in alloc_flags") realized there's a gap for OOM (even if changelog doesn't mention it) but we should allow the order-0 atomic allocations to fallback as well. > --- > mm/page_alloc.c | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > index 8afab64814dc..0c4c359f5ba7 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -2898,7 +2898,7 @@ struct page *rmqueue_buddy(struct zone *preferred_zone, struct zone *zone, > * failing a high-order atomic allocation in the > * future. > */ We should also update the comment above to reflect this is no longer just for the OOM case? > - if (!page && (alloc_flags & ALLOC_OOM)) > + if (!page && (alloc_flags & (ALLOC_OOM|ALLOC_NON_BLOCK))) > page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC); > > if (!page) {