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Fri, 29 Aug 2025 08:36:18 +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 4RKNNIJmsWhRIAAAD6G6ig (envelope-from ); Fri, 29 Aug 2025 08:36:18 +0000 Message-ID: <10cdada2-f28f-4868-b821-4a13ed627e76@suse.cz> Date: Fri, 29 Aug 2025 10:36:18 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm/page_alloc: only set ALLOC_HIGHATOMIC for __GPF_HIGH allocations To: Thadeu Lima de Souza Cascardo , linux-kernel@vger.kernel.org Cc: linux-mm@kvack.org, Andrew Morton , Suren Baghdasaryan , Michal Hocko , Brendan Jackman , Johannes Weiner , Zi Yan , Mel Gorman , kernel-dev@igalia.com, Helen Koike , Matthew Wilcox , Thierry Reding , Sergey Senozhatsky , neil@brown.name References: <20250814172245.1259625-1-cascardo@igalia.com> Content-Language: en-US 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: <20250814172245.1259625-1-cascardo@igalia.com> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Stat-Signature: xetqmd9jxk77bzh1izxrwwsn8ep8fwtx X-Rspam-User: X-Rspamd-Queue-Id: 05F52120006 X-Rspamd-Server: rspam01 X-HE-Tag: 1756456580-140690 X-HE-Meta: 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 rgAzutvO 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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 8/14/25 19:22, Thadeu Lima de Souza Cascardo wrote: > Commit 524c48072e56 ("mm/page_alloc: rename ALLOC_HIGH to > ALLOC_MIN_RESERVE") is the start of a series that explains how __GFP_HIGH, > which implies ALLOC_MIN_RESERVE, is going to be used instead of > __GFP_ATOMIC for high atomic reserves. > > Commit eb2e2b425c69 ("mm/page_alloc: explicitly record high-order atomic > allocations in alloc_flags") introduced ALLOC_HIGHATOMIC for such > allocations of order higher than 0. It still used __GFP_ATOMIC, though. > > Then, commit 1ebbb21811b7 ("mm/page_alloc: explicitly define how __GFP_HIGH > non-blocking allocations accesses reserves") just turned that check for > !__GFP_DIRECT_RECLAIM, ignoring that high atomic reserves were expected to > test for __GFP_HIGH. > > This leads to high atomic reserves being added for high-order GFP_NOWAIT > allocations and others that clear __GFP_DIRECT_RECLAIM, which is > unexpected. Later, those reserves lead to 0-order allocations going to the > slow path and starting reclaim. > > From /proc/pagetypeinfo, without the patch: > > Node 0, zone DMA, type HighAtomic 0 0 0 0 0 0 0 0 0 0 0 > Node 0, zone DMA32, type HighAtomic 1 8 10 9 7 3 0 0 0 0 0 > Node 0, zone Normal, type HighAtomic 64 20 12 5 0 0 0 0 0 0 0 > > With the patch: > > Node 0, zone DMA, type HighAtomic 0 0 0 0 0 0 0 0 0 0 0 > Node 0, zone DMA32, type HighAtomic 0 0 0 0 0 0 0 0 0 0 0 > Node 0, zone Normal, type HighAtomic 0 0 0 0 0 0 0 0 0 0 0 > > Fixes: 1ebbb21811b7 ("mm/page_alloc: explicitly define how __GFP_HIGH non-blocking allocations accesses reserves") > Signed-off-by: Thadeu Lima de Souza Cascardo > Tested-by: Helen Koike > Cc: Mel Gorman > Cc: Michal Hocko > Cc: Matthew Wilcox > Cc: NeilBrown > Cc: Thierry Reding > Cc: Vlastimil Babka Agreed with others that this change matches the original intention and it must have been an oversight. Also found nothing to the contrary in the original threads. > --- > 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 2ef3c07266b3..bf52e3bef626 100644 > --- a/mm/page_alloc.c > +++ b/mm/page_alloc.c > @@ -4219,7 +4219,7 @@ gfp_to_alloc_flags(gfp_t gfp_mask, unsigned int order) > if (!(gfp_mask & __GFP_NOMEMALLOC)) { > alloc_flags |= ALLOC_NON_BLOCK; > > - if (order > 0) > + if (order > 0 && (alloc_flags & ALLOC_MIN_RESERVE)) > alloc_flags |= ALLOC_HIGHATOMIC; > } >