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Mon, 7 Jul 2025 14:14:28 +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 rz6eJUTWa2iOKgAAD6G6ig (envelope-from ); Mon, 07 Jul 2025 14:14:28 +0000 Message-ID: <5a848e15-6a57-4ecb-a015-d4f358b8a5d3@suse.cz> Date: Mon, 7 Jul 2025 16:14:28 +0200 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH] mm, vmstat: remove the NR_WRITEBACK_TEMP node_stat_item counter Content-Language: en-US To: Andrew Morton , "Matthew Wilcox (Oracle)" Cc: Tejun Heo , Maxim Patlasov , Jan Kara , Zach O'Keefe , Jonathan Corbet , Greg Kroah-Hartman , "Rafael J. Wysocki" , Danilo Krummrich , Suren Baghdasaryan , Michal Hocko , "Kirill A. Shutemov" , Brendan Jackman , Johannes Weiner , Zi Yan , Joanne Koong , Jingbo Xu , Jeff Layton , Miklos Szeredi , linux-kernel@vger.kernel.org, linux-fsdevel@vger.kernel.org, linux-doc@vger.kernel.org, linux-mm@kvack.org, Jens Axboe References: <20250625-nr_writeback_removal-v1-1-7f2a0df70faa@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: <20250625-nr_writeback_removal-v1-1-7f2a0df70faa@suse.cz> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 7EA46180010 X-Stat-Signature: zsegepg36gewpwrn3ad9wdsp6jbbcbtf X-Rspam-User: X-HE-Tag: 1751897670-109214 X-HE-Meta: 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 GGHB3cCM Qk4OC5P7P04Lx1tmWOPmaJZ4f86EbFvgyzWZ5mrWGvtp43H5r8g3B4yYDut4sHgTphP05t5CjSKE33qRaxomtIUvfrTDJqikwq2Xk8jGohM69AlcxJRt3ME8Al7umTdPZAwOFAPtqOxTaK199Ysi3MkQvp07uRtgN/Oekw+E1DDz0CMQNwGx6Z0CnLb01tI5GTCWxMVbTS3SLEuycbT+e4jOHORo5e3/J8TtEkX/aAIbSQMrLZNjqAOPtQBEtICOBE3XoQuNyXQgDbp7k4jrS18cBNskEweMsRNI1eiBEvoXKM0s= 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 6/25/25 17:51, Vlastimil Babka wrote: > The only user of the counter (FUSE) was removed in commit 0c58a97f919c > ("fuse: remove tmp folio for writebacks and internal rb tree") so follow > the established pattern of removing the counter and hardcoding 0 in > meminfo output, as done recently with NR_BOUNCE. Update documentation > for procfs, including for the value for Bounce that was missed when > removing its counter. > > Signed-off-by: Vlastimil Babka > --- > The removal of the counter is straightforward. The reason for the large > Cc list is that there is a comment in mm/page-writeback.c function > wb_position_ratio() that mentions NR_WRITEBACK_TEMP, and just deleting > the sentence feels to me it could be the wrong thing to do - maybe the > strictlimit feature itself is now obsolete? It sure does mention FUSE > as the main reason to exist, but commit 5a53748568f79 that introduced it > also mentions slow USB sticks as a possibile scenario. Has that > happened? I'm not familiar enough with this so I'd rather highlight this > and ask for input here than make "git grep NR_WRITEBACK_TEMP" return > nothing. Thanks all for the input. Andrew, please squash in this fixup. The changelog of that can be appended to the changelog of the original patch. Thanks. ----8<---- >From 55d9070995010991abc0c6dbd68a8a53b5d622bc Mon Sep 17 00:00:00 2001 From: Vlastimil Babka Date: Mon, 7 Jul 2025 16:09:31 +0200 Subject: [PATCH] mm, vmstat: remove the NR_WRITEBACK_TEMP node_stat_item counter-fix Also remove the mention of NR_WRITEBACK_TEMP implications from a comment in wb_position_ratio(). The rest of the comment there about fuse setting bdi->max_ratio to 1% is still correct. Signed-off-by: Vlastimil Babka --- mm/page-writeback.c | 4 +--- 1 file changed, 1 insertion(+), 3 deletions(-) diff --git a/mm/page-writeback.c b/mm/page-writeback.c index 72b0ff0d4bae..3e248d1c3969 100644 --- a/mm/page-writeback.c +++ b/mm/page-writeback.c @@ -1101,9 +1101,7 @@ static void wb_position_ratio(struct dirty_throttle_control *dtc) * such filesystems balance_dirty_pages always checks wb counters * against wb limits. Even if global "nr_dirty" is under "freerun". * This is especially important for fuse which sets bdi->max_ratio to - * 1% by default. Without strictlimit feature, fuse writeback may - * consume arbitrary amount of RAM because it is accounted in - * NR_WRITEBACK_TEMP which is not involved in calculating "nr_dirty". + * 1% by default. * * Here, in wb_position_ratio(), we calculate pos_ratio based on * two values: wb_dirty and wb_thresh. Let's consider an example: -- 2.50.0