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Wed, 27 Aug 2025 08:44:37 +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 9rvsLXXFrmjHBQAAD6G6ig (envelope-from ); Wed, 27 Aug 2025 08:44:37 +0000 Message-ID: <36584aaa-7f9b-407b-ad10-64a6ae619235@suse.cz> Date: Wed, 27 Aug 2025 10:44:37 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v3] mm: slub: avoid wake up kswapd in set_track_prepare Content-Language: en-US From: Vlastimil Babka To: Harry Yoo Cc: Matthew Wilcox , yangshiguang1011@163.com, akpm@linux-foundation.org, cl@gentwo.org, rientjes@google.com, roman.gushchin@linux.dev, glittao@gmail.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org, yangshiguang , stable@vger.kernel.org References: <20250825121737.2535732-1-yangshiguang1011@163.com> <54d9e5ac-5a51-4901-9b13-4c248aada2d7@suse.cz> <6be0c134-b5b0-4ff9-9d2a-4b68f22c3762@suse.cz> 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: <6be0c134-b5b0-4ff9-9d2a-4b68f22c3762@suse.cz> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Action: no action X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: A9FEFA0006 X-Stat-Signature: ybkueb7wmm3jic4x4hpu4bs7ebtxmme1 X-Rspam-User: X-HE-Tag: 1756284280-251358 X-HE-Meta: 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 pvqC23Cp XjeUHBhemsHSoTHRLqLa05WB35BGWSWzXO/Y/mF69WBWJiXc26m9sZZyX5afEViG071NP2izMOXndkUB/Wwx1JEaTBt3byy9x8muN0cfh+KMW6UhFcLUxeyJg0IIdhR83k7RqUfHG4Vt/5KbhjPrZNlIGDqzj8PKDq3lZ4XTEhOi1pkWZw0LnYPyfkHC7KcIbHtDu7n4hRDMPYOD5NroERPaTEOKLKAGVloEQZkM89+3PdeLyAoLH58LPfcBAib3VyiJ8feR5BZzvr9O6zw3dV6qcC7GZIsTUbUVMbGQujse+1lTamPkh4KumFr3yXoJYW3GDEVfGceg+Fv/fj1Cx4uYb97pSWwl5ky18fuyfawxO1iFu0fzQMDg1eNsiFTV64HFa 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 8/27/25 10:00, Vlastimil Babka wrote: > On 8/27/25 07:17, Harry Yoo wrote: >> On Mon, Aug 25, 2025 at 05:42:52PM +0200, Vlastimil Babka wrote: >>> On 8/25/25 14:40, Matthew Wilcox wrote: >>> > On Mon, Aug 25, 2025 at 08:17:37PM +0800, yangshiguang1011@163.com wrote: >>> >> Avoid deadlock caused by implicitly waking up kswapd by >>> >> passing in allocation flags. >>> > [...] >>> >> + /* Preemption is disabled in ___slab_alloc() */ >>> >> + gfp_flags &= ~(__GFP_DIRECT_RECLAIM); >>> > >>> > If you don't mean __GFP_KSWAPD_RECLAIM here, the explanation needs to >>> > be better. >>> >>> It was suggested by Harry here: >>> https://lore.kernel.org/all/aKKhUoUkRNDkFYYb@harry >>> >>> I think the comment is enough? Disabling preemption means we can't direct >>> reclaim, but we can wake up kswapd. If the slab caller context is such that >>> we can't, __GFP_KSWAPD_RECLAIM already won't be in the gfp_flags. >> >> To make it a little bit more verbose, this ^^ explanation can be added to the >> changelog? >> >>> But I think we should mask our also __GFP_NOFAIL and add __GFP_NOWARN? >> >> That sounds good. >> >>> (we should get some common helpers for these kinds of gfp flag manipulations >>> already) >> >> Any ideas for its name? >> >> gfp_dont_try_too_hard(), >> gfp_adjust_lightweight(), >> gfp_adjust_mayfail(), >> ... >> >> I'm not good at naming :/ > > Looks like there's already gfp_nested_mask() for these purposes. I'm not > sure if it should be allowing GFP_ATOMIC (thus __GFP_HIGH) as it does > though. Seems to contradict the comment about not exhausing reserves. Wonder > if that was raised during review... Looks like I mentioned it but inconclusively. https://lore.kernel.org/linux-xfs/1fb5b8f3-d8c7-4350-888a-ad8f4d54bc66@suse.cz/ Anyway that's orthogonal to using the helper here right now. > The masking out of __GFP_DIRECT_RECLAIM is specific to the slab case so we > don't need a helper for that (unless we find other users). It could be then > e.g. gfp_nested_mask_noblock() ? >