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Thu, 7 Aug 2025 10:48:43 +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 QS0CKIuElGh3VAAAD6G6ig (envelope-from ); Thu, 07 Aug 2025 10:48:43 +0000 Message-ID: <33275585-f2db-4779-89f0-3ae24b455a67@suse.cz> Date: Thu, 7 Aug 2025 12:48:43 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: Realtime threads delayed due to kcompactd0 Content-Language: en-US To: Alexander Krabler , Frank van der Linden , Mike Galbraith , Hugh Dickins Cc: "linux-rt-users@vger.kernel.org" , "linux-mm@kvack.org" , Dennis Schimmel , Daniel Braunwarth References: <71df781c-3ef3-4b26-9ba8-93fc7d4f9eec@suse.cz> <026de9fcd4f0ed17c2df95c4f7c56b878a844012.camel@gmx.de> <25ba0d77-eb61-4efc-b2fc-73878cbd85c1@suse.cz> 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: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Queue-Id: 500E7180006 X-Stat-Signature: nta83nek77xny8xt9j3zz6sqhbidr9ui X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1754563725-741099 X-HE-Meta: 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 7i7LKG6r 9dAXishu61s5LA6Z2F+0IUJ3qsoCuL+fqZgn52GhMHiOE4dT8IsaET61wo/KjT1QWgXwT4NbkS0Q09Uu8K8YGAsorraS569H//WzD4YFdvhsqqaulIt+wr73pAuX+Br4MMaQH1az2jlI/NiNA9r8lHc5WRYflgToiD6dXPmKoZ9a64deOrkWR+D95RGYY2TJgLh+oZmy5tLTpd0iYfnf/BHtHCIDmSdKXfTgR7Ls6v1G0oR5DELFfRB2uAHQieIRdNxhXCRdsb60dBhA3lAakyCVV7XQz0/u/amL6qdAXYpt/c8ClykwtJcnbfSYR9eLjIovp4ERqCa0Hpczby6dxujF3V9TrRsjzo4Dwi11qjzLSaFwNF/mX7tbv8UTXDdH6TxUs0nTgaWpO2pnNpi0GWQrEX0hpo9EKVf5n6Grke60dSrTcrOVnQOPviQ== 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 8/1/25 15:40, Alexander Krabler wrote: > On 8/1/25 14:57, Vlastimil Babka wrote: >> Hm that means something isn't working as intended. Do the pages have also >> the unevictable flag? > > I have checked /proc//smaps. > Neither the manpage (https://www.man7.org/linux/man-pages/man5/proc_pid_smaps.5.html) > nor kernel source code (fs/proc/task_mmu.c show_smap_vma_flags) tells me about unevictable flag. Ah ok, you checked /proc/pid/smaps. Since you said "pages" I thought you meant individual pages which would be from /proc/kpageflags But IIRC getting a page in a state where it has an mlock flag but (not yet) the unevictable flag should be rare so I would be surprised if that was the problem here. Hm or maybe it's actually that the error can happen only in the other direction - page is unevictable (on unevictable list) while not mlocked, at least the counters such as UNEVICTABLE_PGRESCUED suggest that. Hugh knows this code the best. Do you think we should e.g. test the mlocked flag instead/in addition to unevictable flag in compaction to avoid violating vm.compact_unevictable_allowed = 0?