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 AA104CD3447 for ; Sat, 9 May 2026 10:19:49 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 9F9096B0314; Sat, 9 May 2026 06:19:48 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 9A9B76B0315; Sat, 9 May 2026 06:19:48 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 871B86B0316; Sat, 9 May 2026 06:19:48 -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 75D0A6B0314 for ; Sat, 9 May 2026 06:19:48 -0400 (EDT) Received: from smtpin05.hostedemail.com (lb01a-stub [10.200.18.249]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 19CCB8D373 for ; Sat, 9 May 2026 10:19:48 +0000 (UTC) X-FDA: 84747485256.05.B5DA064 Received: from tor.source.kernel.org (tor.source.kernel.org [172.105.4.254]) by imf24.hostedemail.com (Postfix) with ESMTP id 471D5180005 for ; Sat, 9 May 2026 10:19:46 +0000 (UTC) Authentication-Results: imf24.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=MgQ8l6Q5; spf=pass (imf24.hostedemail.com: domain of jlayton@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=jlayton@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1778321986; h=from:from:sender:reply-to:subject:subject:date:date: message-id:message-id:to:to:cc:cc:mime-version:mime-version: content-type:content-type: content-transfer-encoding:content-transfer-encoding: in-reply-to:in-reply-to:references:references:dkim-signature; bh=ALGcroP4NAi2ExMLqaI6PAnKBqGcuU5COvma6qEzmns=; b=ATEShsBq8UcdonIzFao0X6rfUJIa7D8ugY3Lvw21d6SuPSIFjTnXab/DEDqG+v7UjE9n2z bV7+YpUjGps3x7igrVoOqYz/gJWZ92E5AAH9JGzf1KmegPJQ7GhL1HwGWD1hpLpzm6iRTX ryF0Iq2PfpN5QiydYFC6WbDbgxa0BeI= ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1778321986; a=rsa-sha256; cv=none; b=IWYeSLN/2t6tpwfkZNrSlYKzAbx/7xiu4AcjzKSZYbVRsPaP50YWx6mRYR1OEubp1xFCTi /ags12vVohgviyhfJ8Pl6MtCDTGyKLbEh+qUtIyrn8Q8n+/Lx/+laOL3cJc3kvOCE22VKT kCdUjqvhfhzf5irj/nPfIZpAnRA9Ipo= ARC-Authentication-Results: i=1; imf24.hostedemail.com; dkim=pass header.d=kernel.org header.s=k20201202 header.b=MgQ8l6Q5; spf=pass (imf24.hostedemail.com: domain of jlayton@kernel.org designates 172.105.4.254 as permitted sender) smtp.mailfrom=jlayton@kernel.org; dmarc=pass (policy=quarantine) header.from=kernel.org Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by tor.source.kernel.org (Postfix) with ESMTP id A8A486057A; Sat, 9 May 2026 10:19:45 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 90F2EC2BCB4; Sat, 9 May 2026 10:19:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1778321985; bh=5/Lh2DOlxoyMERzAlFtWE/g8RwDjiTeHdspXWqs4RP8=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=MgQ8l6Q5BGS6CYCsHSFa47YdvcQfjVhzVuaPUa0LmHo0YSDKtZxGbgjH6PTcA6965 cCW2wRSaUJ9sneDvJxLl/BYPCS+YngyI6tRheTJUywbsSJRmCn9t495Z3n2YVgj1CC 9LT7uxxsEsOg+Glm7xSpaMVl/JlM0CKKD703grzDvpkVrQvRoLPYJw9qBVZA4OWPwK WcsuWQVU7dR/MK5U+248iYU7EYkA28Yw/QY2e4aGUfG5tskj0JVQeQFs1sxu+w4aXQ tVXf08AK5ob3Nq9NB1Rkf879kqjm/6hRrywcbrM01iErOYbPYBNSfdOSEhF4XSkdEw uOth1A+N37uRA== Message-ID: Subject: Re: [PATCH v6 2/2] mm: kick writeback flusher for IOCB_DONTCACHE with targeted dirty tracking From: Jeff Layton To: Andrew Morton Cc: Alexander Viro , Christian Brauner , Jan Kara , "Matthew Wilcox (Oracle)" , David Hildenbrand , Lorenzo Stoakes , "Liam R. Howlett" , Vlastimil Babka , Mike Rapoport , Suren Baghdasaryan , Michal Hocko , Mike Snitzer , Jens Axboe , Ritesh Harjani , Chuck Lever , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, linux-nfs@vger.kernel.org, linux-mm@kvack.org Date: Sat, 09 May 2026 06:19:40 -0400 In-Reply-To: <20260508172014.8265ddc0220ff7e4d54674ff@linux-foundation.org> References: <20260505-dontcache-v6-0-66463805dd6a@kernel.org> <20260505-dontcache-v6-2-66463805dd6a@kernel.org> <20260508172014.8265ddc0220ff7e4d54674ff@linux-foundation.org> Autocrypt: addr=jlayton@kernel.org; prefer-encrypt=mutual; keydata=mQINBE6V0TwBEADXhJg7s8wFDwBMEvn0qyhAnzFLTOCHooMZyx7XO7dAiIhDSi7G1NPxw n8jdFUQMCR/GlpozMFlSFiZXiObE7sef9rTtM68ukUyZM4pJ9l0KjQNgDJ6Fr342Htkjxu/kFV1Wv egyjnSsFt7EGoDjdKqr1TS9syJYFjagYtvWk/UfHlW09X+jOh4vYtfX7iYSx/NfqV3W1D7EDi0PqV T2h6v8i8YqsATFPwO4nuiTmL6I40ZofxVd+9wdRI4Db8yUNA4ZSP2nqLcLtFjClYRBoJvRWvsv4lm 0OX6MYPtv76hka8lW4mnRmZqqx3UtfHX/hF/zH24Gj7A6sYKYLCU3YrI2Ogiu7/ksKcl7goQjpvtV YrOOI5VGLHge0awt7bhMCTM9KAfPc+xL/ZxAMVWd3NCk5SamL2cE99UWgtvNOIYU8m6EjTLhsj8sn VluJH0/RcxEeFbnSaswVChNSGa7mXJrTR22lRL6ZPjdMgS2Km90haWPRc8Wolcz07Y2se0xpGVLEQ cDEsvv5IMmeMe1/qLZ6NaVkNuL3WOXvxaVT9USW1+/SGipO2IpKJjeDZfehlB/kpfF24+RrK+seQf CBYyUE8QJpvTZyfUHNYldXlrjO6n5MdOempLqWpfOmcGkwnyNRBR46g/jf8KnPRwXs509yAqDB6sE LZH+yWr9LQZEwARAQABtCVKZWZmIExheXRvbiA8amxheXRvbkBwb29jaGllcmVkcy5uZXQ+iQI7BB MBAgAlAhsDBgsJCAcDAgYVCAIJCgsEFgIDAQIeAQIXgAUCTpXWPAIZAQAKCRAADmhBGVaCFc65D/4 gBLNMHopQYgG/9RIM3kgFCCQV0pLv0hcg1cjr+bPI5f1PzJoOVi9s0wBDHwp8+vtHgYhM54yt43uI 7Htij0RHFL5eFqoVT4TSfAg2qlvNemJEOY0e4daljjmZM7UtmpGs9NN0r9r50W82eb5Kw5bc/r0km R/arUS2st+ecRsCnwAOj6HiURwIgfDMHGPtSkoPpu3DDp/cjcYUg3HaOJuTjtGHFH963B+f+hyQ2B rQZBBE76ErgTDJ2Db9Ey0kw7VEZ4I2nnVUY9B5dE2pJFVO5HJBMp30fUGKvwaKqYCU2iAKxdmJXRI ONb7dSde8LqZahuunPDMZyMA5+mkQl7kpIpR6kVDIiqmxzRuPeiMP7O2FCUlS2DnJnRVrHmCljLkZ Wf7ZUA22wJpepBligemtSRSbqCyZ3B48zJ8g5B8xLEntPo/NknSJaYRvfEQqGxgk5kkNWMIMDkfQO lDSXZvoxqU9wFH/9jTv1/6p8dHeGM0BsbBLMqQaqnWiVt5mG92E1zkOW69LnoozE6Le+12DsNW7Rj iR5K+27MObjXEYIW7FIvNN/TQ6U1EOsdxwB8o//Yfc3p2QqPr5uS93SDDan5ehH59BnHpguTc27Xi QQZ9EGiieCUx6Zh2ze3X2UW9YNzE15uKwkkuEIj60NvQRmEDfweYfOfPVOueC+iFifbQgSmVmZiBM YXl0b24gPGpsYXl0b25AcmVkaGF0LmNvbT6JAjgEEwECACIFAk6V0q0CGwMGCwkIBwMCBhUIAgkKC wQWAgMBAh4BAheAAAoJEAAOaEEZVoIViKUQALpvsacTMWWOd7SlPFzIYy2/fjvKlfB/Xs4YdNcf9q LqF+lk2RBUHdR/dGwZpvw/OLmnZ8TryDo2zXVJNWEEUFNc7wQpl3i78r6UU/GUY/RQmOgPhs3epQC 3PMJj4xFx+VuVcf/MXgDDdBUHaCTT793hyBeDbQuciARDJAW24Q1RCmjcwWIV/pgrlFa4lAXsmhoa c8UPc82Ijrs6ivlTweFf16VBc4nSLX5FB3ls7S5noRhm5/Zsd4PGPgIHgCZcPgkAnU1S/A/rSqf3F LpU+CbVBDvlVAnOq9gfNF+QiTlOHdZVIe4gEYAU3CUjbleywQqV02BKxPVM0C5/oVjMVx3bri75n1 TkBYGmqAXy9usCkHIsG5CBHmphv9MHmqMZQVsxvCzfnI5IO1+7MoloeeW/lxuyd0pU88dZsV/riHw 87i2GJUJtVlMl5IGBNFpqoNUoqmvRfEMeXhy/kUX4Xc03I1coZIgmwLmCSXwx9MaCPFzV/dOOrju2 xjO+2sYyB5BNtxRqUEyXglpujFZqJxxau7E0eXoYgoY9gtFGsspzFkVNntamVXEWVVgzJJr/EWW0y +jNd54MfPRqH+eCGuqlnNLktSAVz1MvVRY1dxUltSlDZT7P2bUoMorIPu8p7ZCg9dyX1+9T6Muc5d Hxf/BBP/ir+3e8JTFQBFOiLNdFtB9KZWZmIExheXRvbiA8amxheXRvbkBzYW1iYS5vcmc+iQI4BBM BAgAiBQJOldK9AhsDBgsJCAcDAgYVCAIJCgsEFgIDAQIeAQIXgAAKCRAADmhBGVaCFWgWD/0ZRi4h N9FK2BdQs9RwNnFZUr7JidAWfCrs37XrA/56olQl3ojn0fQtrP4DbTmCuh0SfMijB24psy1GnkPep naQ6VRf7Dxg/Y8muZELSOtsv2CKt3/02J1BBitrkkqmHyni5fLLYYg6fub0T/8Kwo1qGPdu1hx2BQ RERYtQ/S5d/T0cACdlzi6w8rs5f09hU9Tu4qV1JLKmBTgUWKN969HPRkxiojLQziHVyM/weR5Reu6 FZVNuVBGqBD+sfk/c98VJHjsQhYJijcsmgMb1NohAzwrBKcSGKOWJToGEO/1RkIN8tqGnYNp2G+aR 685D0chgTl1WzPRM6mFG1+n2b2RR95DxumKVpwBwdLPoCkI24JkeDJ7lXSe3uFWISstFGt0HL8Eew P8RuGC8s5h7Ct91HMNQTbjgA+Vi1foWUVXpEintAKgoywaIDlJfTZIl6Ew8ETN/7DLy8bXYgq0Xzh aKg3CnOUuGQV5/nl4OAX/3jocT5Cz/OtAiNYj5mLPeL5z2ZszjoCAH6caqsF2oLyAnLqRgDgR+wTQ T6gMhr2IRsl+cp8gPHBwQ4uZMb+X00c/Amm9VfviT+BI7B66cnC7Zv6Gvmtu2rEjWDGWPqUgccB7h dMKnKDthkA227/82tYoFiFMb/NwtgGrn5n2vwJyKN6SEoygGrNt0SI84y6hEVbQlSmVmZiBMYXl0b 24gPGpsYXl0b25AcHJpbWFyeWRhdGEuY29tPokCOQQTAQIAIwUCU4xmKQIbAwcLCQgHAwIBBhUIAg kKCwQWAgMBAh4BAheAAAoJEAAOaEEZVoIV1H0P/j4OUTwFd7BBbpoSp695qb6HqCzWMuExsp8nZjr uymMaeZbGr3OWMNEXRI1FWNHMtcMHWLP/RaDqCJil28proO+PQ/yPhsr2QqJcW4nr91tBrv/MqItu AXLYlsgXqp4BxLP67bzRJ1Bd2x0bWXurpEXY//VBOLnODqThGEcL7jouwjmnRh9FTKZfBDpFRaEfD FOXIfAkMKBa/c9TQwRpx2DPsl3eFWVCNuNGKeGsirLqCxUg5kWTxEorROppz9oU4HPicL6rRH22Ce 6nOAON2vHvhkUuO3GbffhrcsPD4DaYup4ic+DxWm+DaSSRJ+e1yJvwi6NmQ9P9UAuLG93S2MdNNbo sZ9P8k2mTOVKMc+GooI9Ve/vH8unwitwo7ORMVXhJeU6Q0X7zf3SjwDq2lBhn1DSuTsn2DbsNTiDv qrAaCvbsTsw+SZRwF85eG67eAwouYk+dnKmp1q57LDKMyzysij2oDKbcBlwB/TeX16p8+LxECv51a sjS9TInnipssssUDrHIvoTTXWcz7Y5wIngxDFwT8rPY3EggzLGfK5Zx2Q5S/N0FfmADmKknG/D8qG IcJE574D956tiUDKN4I+/g125ORR1v7bP+OIaayAvq17RP+qcAqkxc0x8iCYVCYDouDyNvWPGRhbL UO7mlBpjW9jK9e2fvZY9iw3QzIPGKtClKZWZmIExheXRvbiA8amVmZi5sYXl0b25AcHJpbWFyeWRh dGEuY29tPokCOQQTAQIAIwUCU4xmUAIbAwcLCQgHAwIBBhUIAgkKCwQWAgMBAh4BAheAAAoJEAAOa EEZVoIVzJoQALFCS6n/FHQS+hIzHIb56JbokhK0AFqoLVzLKzrnaeXhE5isWcVg0eoV2oTScIwUSU apy94if69tnUo4Q7YNt8/6yFM6hwZAxFjOXR0ciGE3Q+Z1zi49Ox51yjGMQGxlakV9ep4sV/d5a50 M+LFTmYSAFp6HY23JN9PkjVJC4PUv5DYRbOZ6Y1+TfXKBAewMVqtwT1Y+LPlfmI8dbbbuUX/kKZ5d dhV2736fgyfpslvJKYl0YifUOVy4D1G/oSycyHkJG78OvX4JKcf2kKzVvg7/Rnv+AueCfFQ6nGwPn 0P91I7TEOC4XfZ6a1K3uTp4fPPs1Wn75X7K8lzJP/p8lme40uqwAyBjk+IA5VGd+CVRiyJTpGZwA0 jwSYLyXboX+Dqm9pSYzmC9+/AE7lIgpWj+3iNisp1SWtHc4pdtQ5EU2SEz8yKvDbD0lNDbv4ljI7e flPsvN6vOrxz24mCliEco5DwhpaaSnzWnbAPXhQDWb/lUgs/JNk8dtwmvWnqCwRqElMLVisAbJmC0 BhZ/Ab4sph3EaiZfdXKhiQqSGdK4La3OTJOJYZphPdGgnkvDV9Pl1QZ0ijXQrVIy3zd6VCNaKYq7B AKidn5g/2Q8oio9Tf4XfdZ9dtwcB+bwDJFgvvDYaZ5bI3ln4V3EyW5i2NfXazz/GA/I/ZtbsigCFc 8ftCBKZWZmIExheXRvbiA8amxheXRvbkBrZXJuZWwub3JnPokCOAQTAQIAIgUCWe8u6AIbAwYLCQg HAwIGFQgCCQoLBBYCAwECHgECF4AACgkQAA5oQRlWghUuCg/+Lb/xGxZD2Q1oJVAE37uW308UpVSD 2tAMJUvFTdDbfe3zKlPDTuVsyNsALBGclPLagJ5ZTP+Vp2irAN9uwBuacBOTtmOdz4ZN2tdvNgozz uxp4CHBDVzAslUi2idy+xpsp47DWPxYFIRP3M8QG/aNW052LaPc0cedYxp8+9eiVUNpxF4SiU4i9J DfX/sn9XcfoVZIxMpCRE750zvJvcCUz9HojsrMQ1NFc7MFT1z3MOW2/RlzPcog7xvR5ENPH19ojRD CHqumUHRry+RF0lH00clzX/W8OrQJZtoBPXv9ahka/Vp7kEulcBJr1cH5Wz/WprhsIM7U9pse1f1g Yy9YbXtWctUz8uvDR7shsQxAhX3qO7DilMtuGo1v97I/Kx4gXQ52syh/w6EBny71CZrOgD6kJwPVV AaM1LRC28muq91WCFhs/nzHozpbzcheyGtMUI2Ao4K6mnY+3zIuXPygZMFr9KXE6fF7HzKxKuZMJO aEZCiDOq0anx6FmOzs5E6Jqdpo/mtI8beK+BE7Va6ni7YrQlnT0i3vaTVMTiCThbqsB20VrbMjlhp f8lfK1XVNbRq/R7GZ9zHESlsa35ha60yd/j3pu5hT2xyy8krV8vGhHvnJ1XRMJBAB/UYb6FyC7S+m QZIQXVeAA+smfTT0tDrisj1U5x6ZB9b3nBg65kc= Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable User-Agent: Evolution 3.58.3 (3.58.3-1.fc43) MIME-Version: 1.0 X-Rspamd-Server: rspam09 X-Rspamd-Queue-Id: 471D5180005 X-Rspam-User: X-Stat-Signature: gbeshjyizgpffjjac444axdbaf5pzwfd X-HE-Tag: 1778321986-842192 X-HE-Meta: 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 Im21P//E AgTxGYjhyp+nsBmrG6s+XJLpJfi3+JjbuJvBpFF5yR+KxCQwqy+u5/jmPGF9wiJoQBDF0gLylo/+cGX+gST1cRSSusk4Hx/ZCfGuwToaQkYJpscmt91bwp+goZLe5RBKO7g2d2EWvMo8UPVrOrefj1BneXowWOK5fe2nQXeUFzZaq20BsFJTnVRCqSNHeagbyhU034Tl1Ku9gMwY8SNw0pCLJoapBAG/KLDHEml+xVWHsVwNsLQYUiA3O6GDPmN+Xtu49eH49KJi188vIdORqcI6iwZ7PTre/rwfQRWJr/WdgjUktNxcIygT1C5Z1bgDpwBKHC9epOPvbfrGZiJlWT/PxdOg0yVUjS02LNW9oiS6hvxNnBhODKHmfL32kRvfGrENL+pv+rxyBGBMOdzyVVCtf93gblY6oNh2PPLH8hNxqYNI= Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Fri, 2026-05-08 at 17:20 -0700, Andrew Morton wrote: > On Tue, 05 May 2026 20:59:49 +0200 Jeff Layton wrote= : >=20 > > The IOCB_DONTCACHE writeback path in generic_write_sync() calls > > filemap_flush_range() on every write, submitting writeback inline in > > the writer's context. Perf lock contention profiling shows the > > performance problem is not lock contention but the writeback submission > > work itself =E2=80=94 walking the page tree and submitting I/O blocks t= he writer > > for milliseconds, inflating p99.9 latency from 23ms (buffered) to 93ms > > (dontcache). > >=20 > > Replace the inline filemap_flush_range() call with a flusher kick that > > drains dirty pages in the background. This moves writeback submission > > completely off the writer's hot path. > >=20 > > ... > >=20 > > Before After Change > > seq-write/dontcache 298 897 +201% > > rand-write/dontcache 131 236 +80% > >=20 > > 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%) > >=20 > > 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% > >=20 > > 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% > >=20 > > Dontcache now reaches 81% of buffered throughput (was 35%). > >=20 > > 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 > >=20 > > ... > >=20 > > 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. > >=20 > > 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. >=20 > Geeze, is that the best you can do ;) >=20 > Sashiko seems to have found more stuff: > https://sashiko.dev/#/patchset/20260505-dontcache-v6-0-66463805dd6a@kern= el.org I saw those after I sent the last set and have been working on addressing them. I've also found a couple more via dueling Gemini and Claude reviews. I'll have a v7 posting coming early next week. Thanks, --=20 Jeff Layton