From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 05AA6CD343F for ; Wed, 13 May 2026 03:07:12 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 729896B0092; Tue, 12 May 2026 23:07:11 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 6D9686B0093; Tue, 12 May 2026 23:07:11 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 5F00D6B0095; Tue, 12 May 2026 23:07:11 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0016.hostedemail.com [216.40.44.16]) by kanga.kvack.org (Postfix) with ESMTP id 4DD436B0092 for ; Tue, 12 May 2026 23:07:11 -0400 (EDT) Received: from smtpin25.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay02.hostedemail.com (Postfix) with ESMTP id F31B81206AC for ; Wed, 13 May 2026 03:07:10 +0000 (UTC) X-FDA: 84760910220.25.EEF84DB Received: from mail-pg1-f170.google.com (mail-pg1-f170.google.com [209.85.215.170]) by imf12.hostedemail.com (Postfix) with ESMTP id 40C3C40002 for ; Wed, 13 May 2026 03:07:09 +0000 (UTC) Authentication-Results: imf12.hostedemail.com; dkim=pass header.d=gmail.com header.s=20251104 header.b=g1O25Pyj; spf=pass (imf12.hostedemail.com: domain of ritesh.list@gmail.com designates 209.85.215.170 as permitted sender) smtp.mailfrom=ritesh.list@gmail.com; dmarc=pass (policy=none) header.from=gmail.com ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1778641629; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:content-type: content-transfer-encoding:in-reply-to:in-reply-to: references:references:dkim-signature; bh=mr8B54nCUqKe73fttlmYFbpBv8yytDHMFbs5Gt5TGns=; b=JuKx9Rxkxq9rd6ilBG8gH4InonnRS0fVf3Nz8ErHYCf0N77XiDq65ho8rUIN1SMXg7zdtp nPp2VV9MRJxXuq2GoI/Ue+OPV3h0cHqPuxDCzdxw36RYbxdhyRKglWgC/+ngUZweiyn756 5n1I4S+JvnY8fzulGme9QTiUCYCRgbk= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1778641629; a=rsa-sha256; cv=none; b=DFEFiD2krYBjAHT9+JRp5oRyVAvnG+piGs7pfDStjZlAs/RrcSTnKz0hqlCH86ya6ddHRf LfxMzWfPzr66zIvxs2yjAeI68cAm4QTIEISqf8GaiGhMpvifzEE8Ou2OoUu34BPipEuL+V CNHwwE0leC2mLquD366EEr6j6v+birg= ARC-Authentication-Results: i=1; imf12.hostedemail.com; dkim=pass header.d=gmail.com header.s=20251104 header.b=g1O25Pyj; spf=pass (imf12.hostedemail.com: domain of ritesh.list@gmail.com designates 209.85.215.170 as permitted sender) smtp.mailfrom=ritesh.list@gmail.com; dmarc=pass (policy=none) header.from=gmail.com Received: by mail-pg1-f170.google.com with SMTP id 41be03b00d2f7-c82471904fcso2721065a12.2 for ; Tue, 12 May 2026 20:07:09 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20251104; t=1778641628; x=1779246428; darn=kvack.org; h=references:message-id:date:in-reply-to:subject:cc:to:from:from:to :cc:subject:date:message-id:reply-to; bh=mr8B54nCUqKe73fttlmYFbpBv8yytDHMFbs5Gt5TGns=; b=g1O25PyjixheMax/EA79h0PjV0Ch5BRIlHXBVNrZOc4rTObKiP9iz/ioqGRc1G4c2T XQFucCAEeWwh8JuEPAKjeFrWylFJKZFX/eGMKdHUEqYY5OhrTL+j3pIcfGE/R9nuHfZi SU8TnqHpX/FiFEgGABp446SmQ8BIrQQ3whd5RYp0NoZY33B/TGPCywYm7ZSgJ6ukb+vb vNGqPx2JhUhq5JXpbqQHm4/KIrK8humXf+UlwnJrLMn+AzAk49N4IArYfWMOEYEdDuyU qnZETd4JfaE9PMWQRwcqPv2ZivyIfPOPYqvzGOKRxLECTaSHEooCUHRlaihfH5v8QPmI cE+w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20251104; t=1778641628; x=1779246428; h=references:message-id:date:in-reply-to:subject:cc:to:from:x-gm-gg :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=mr8B54nCUqKe73fttlmYFbpBv8yytDHMFbs5Gt5TGns=; b=aY/uZ7kq2olXOxEyP9XV7eFMtLYj8f4CcKi94zUqUzjmfeR/LyrIvNrYKUxaMYHvob S6RwxWquwKf8V6YoCEF/hByqBBxLTNF4ZhL/FwNODq/668aP/uIKtRnl3j4T4CEnm8/A aLlxyBuY2W1XrIQ/5mFhTTNOL4IDvrPC4wo9Azb9Q7m/1DAJ8omnpjU8/4UsUr04amtQ +M4eeW5fMTn2n9Bx/RP2HsPRKRh1ZItJbBboZVRiU0rklAaWBydsSv8+R1Ksj8boOPDk mqJDdb03fMwRJdgRbUyFC950hZLpaId4s/4Y2pROoFcHd01hE1t+hGh6B/4RJgCtmdXk mi6g== X-Forwarded-Encrypted: i=1; AFNElJ87PzefhsqbtRgtt2KiQ6D6myCHSxSRW5UFWHQGCkhZ+v/boJcU1YsHVg0D23UKym1P6pVg7l8vxg==@kvack.org X-Gm-Message-State: AOJu0YzF1jyn785JWmOlSxOUFCe05gl30Rl35VgbHDHz7wBohwXZbzKh dGy69OqKhqGw3mH7dL6Luc17kp2q1KUKvw+9RBZxnTt53zYu/D7Q+MVQ X-Gm-Gg: Acq92OHzVFJhpqsMkRR/OfrPws+5f7BArLcBnrbqjoVJkpTSGFhTs3P5X7OK6KMHPQi XzCEfUiNV+bNPuNNfrLa+20DxBwSP6oyfAxqh8UHL0dwhtjxtxI5vEmpf3KmaSFjCqp493qo6Sv bBG9WBiUiQZjstA8rKSeSGuoZuni7aRJAgpfdxi6zLRKALW0L/A0HMbn3l8ol9tKL4+4VPMweO1 WKdNe6FRHwkdfcp5nN9TiUh6eip8HRNkGpz2zw8BjRbD3VozMiehCIaqPuZKijQrtiTrGsAlIgg md2AVFViAuzF5gjlmpE4hLcTeB2Yh7It2CHW7QeddLUKiGA/dhcWE1eX+Eo2nvDzORzvQjF58Ec q3t4+/j/oimpkhT7A9c05FnbFI5aaLeTeVM+DQ0tLWZXuHxoRGJwRXYj9KzVwJHnh9dB6B8hj5N CCmAl2KqQZ7gs1QUSaGShOhq0upl1N/2tI X-Received: by 2002:a05:6a00:4146:b0:82a:17b8:1474 with SMTP id d2e1a72fcca58-83f03e92ea5mr1356854b3a.1.1778641627973; Tue, 12 May 2026 20:07:07 -0700 (PDT) Received: from pve-server ([49.205.216.49]) by smtp.gmail.com with ESMTPSA id d2e1a72fcca58-839685a3187sm25369465b3a.60.2026.05.12.20.07.01 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 12 May 2026 20:07:07 -0700 (PDT) From: Ritesh Harjani (IBM) To: Jeff Layton , Alexander Viro , Christian Brauner , Jan Kara , "Matthew Wilcox (Oracle)" , Andrew Morton , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Mike Snitzer , Jens Axboe , Chuck Lever Cc: linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-mm@kvack.org, Jeff Layton Subject: Re: [PATCH v7 3/3] mm: kick writeback flusher for IOCB_DONTCACHE with targeted dirty tracking In-Reply-To: <20260511-dontcache-v7-3-2848ddce8090@kernel.org> Date: Wed, 13 May 2026 08:31:23 +0530 Message-ID: References: <20260511-dontcache-v7-0-2848ddce8090@kernel.org> <20260511-dontcache-v7-3-2848ddce8090@kernel.org> X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 40C3C40002 X-Rspam-User: X-Stat-Signature: 9ex7fukjpnequoh8bfmrt336m8r96f86 X-HE-Tag: 1778641629-218531 X-HE-Meta: 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 mj1Xc211 txa2KIJlB5XsEaivrGHxvhxx7FuyFDoHRdqr9P0Umm1yu3/1KUTzGyOyyFivWHH4MYZ1MDVO2ampfbPsc8vuGSRfSwbuUCiZ/vV5TVCmJRMW4mUF5To8TOevFhGnuYcSILDyWt7MkG6hx1jb/4m69Lcm3onPr/UlcJInyB2uA9DTDnOgTdq586o5u3tBGvQgwxmMqxY57IqPhH3GaLt32AkC1y0+5zeUtnUUSpcAdL8pGei6E+cD/1Qsw6ABulT1poAM6NiCY4D7Hj++hfXc98CKfmARzpf3ghiykCQBJTIrBlFZ/0eNLGAMSXNWcwMAr7ahdeS87ZgfAZcRExKcaTP/0KMrvlRYdn8Kx0Cp0PjGOFps6+Uc9/bsmL1U1JcAa/Dg/El36yqktqmnTpWuRy3iu8g75pSZQY6e6YUmZ+pyT3XeBKLqXIwxj/l6vLMHv5sunK148/RSVHP3jovPo6Jn/8yxBmI5VWvt9 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: Jeff Layton writes: > dontcache-bench results (same host, T6F_SKL_1920GBF, 251 GiB RAM, > xfs on NVMe, fio io_uring): > > Buffered and direct I/O paths are unaffected by this patchset. All > improvements are confined to the dontcache path: > > Single-stream throughput (MB/s): > Before After Change > seq-write/dontcache 298 897 +201% > rand-write/dontcache 131 236 +80% > > Tail latency improvements (seq-write/dontcache): > p99: 135,266 us -> 23,986 us (-82%) > p99.9: 8,925,479 us -> 28,443 us (-99.7%) > > Multi-writer (4 jobs, sequential write): > Before After Change > dontcache aggregate (MB/s) 2,529 4,532 +79% > dontcache p99 (us) 8,553 1,002 -88% > dontcache p99.9 (us) 109,314 1,057 -99% > > Dontcache multi-writer throughput now matches buffered (4,532 vs > 4,616 MB/s). > > 32-file write (Axboe test): > Before After Change > dontcache aggregate (MB/s) 1,548 3,499 +126% > dontcache p99 (us) 10,170 602 -94% > Peak dirty pages (MB) 1,837 213 -88% > > Dontcache now reaches 81% of buffered throughput (was 35%). > > Competing writers (dontcache vs buffered, separate files): > Before After > buffered writer 868 433 MB/s > dontcache writer 415 433 MB/s > Aggregate 1,284 866 MB/s > > Previously the buffered writer starved the dontcache writer 2:1. > With per-bdi_writeback tracking, both writers now receive equal > bandwidth. The aggregate matches the buffered-vs-buffered baseline > (863 MB/s), indicating fair sharing regardless of I/O mode. > > The dontcache writer's p99.9 latency collapsed from 119 ms to > 33 ms (-73%), eliminating the severe periodic stalls seen in the > baseline. Both writers now share identical latency profiles, > matching the buffered-vs-buffered pattern. > > The per-bdi_writeback dirty tracking dramatically reduces peak dirty > pages in dontcache workloads, with the 32-file test dropping from > 1.8 GB to 213 MB. Dontcache sequential write throughput triples and > multi-writer throughput reaches parity with buffered I/O, with tail > latencies collapsing by 1-2 orders of magnitude. > Thanks for also considering multiple request for performance numbers into account, this indeed is a nice improvement overall to RWF_DONTCACHE. With Christian simplification - the patch looks good to me. So, please feel free to add: Reviewed-by: Ritesh Harjani (IBM)