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]) by smtp.lore.kernel.org (Postfix) with ESMTP id B813ED5AE5A for ; Thu, 7 Nov 2024 04:06:58 +0000 (UTC) Received: by kanga.kvack.org (Postfix) id 3C5206B0089; Wed, 6 Nov 2024 23:06:58 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 375886B008A; Wed, 6 Nov 2024 23:06:58 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 23C756B008C; Wed, 6 Nov 2024 23:06:58 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from relay.hostedemail.com (smtprelay0013.hostedemail.com [216.40.44.13]) by kanga.kvack.org (Postfix) with ESMTP id 043AD6B0089 for ; Wed, 6 Nov 2024 23:06:57 -0500 (EST) Received: from smtpin04.hostedemail.com (a10.router.float.18 [10.200.18.1]) by unirelay09.hostedemail.com (Postfix) with ESMTP id 6CBC78035F for ; Thu, 7 Nov 2024 04:06:57 +0000 (UTC) X-FDA: 82757962602.04.86A6F05 Received: from dfw.source.kernel.org (dfw.source.kernel.org [139.178.84.217]) by imf06.hostedemail.com (Postfix) with ESMTP id B4822180005 for ; Thu, 7 Nov 2024 04:06:30 +0000 (UTC) Authentication-Results: imf06.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=pD7qkuYT; dmarc=none; spf=pass (imf06.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org ARC-Message-Signature: i=1; a=rsa-sha256; c=relaxed/relaxed; d=hostedemail.com; s=arc-20220608; t=1730952246; 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=ciNCY5hCrAoNqRLHQaNwmlUW06IlArgfPllXjgXx0Ho=; b=h3oxbtbzZyuZLd0x4Rm54M/Qp0CFrArsnE9OOcJAYtS5B+K82KwwZ636q99wokaO0cgOAu BtnyQ5EMCFO4XxVXW47cw/l/V4yrBpTivD2VKHyteyBBdSTsuQ3AJpm8LVYDhYsArzPA+R M/wsYWLyHH2ipAj9EQoSpIKaO0DMc2o= ARC-Authentication-Results: i=1; imf06.hostedemail.com; dkim=pass header.d=linux-foundation.org header.s=korg header.b=pD7qkuYT; dmarc=none; spf=pass (imf06.hostedemail.com: domain of akpm@linux-foundation.org designates 139.178.84.217 as permitted sender) smtp.mailfrom=akpm@linux-foundation.org ARC-Seal: i=1; s=arc-20220608; d=hostedemail.com; t=1730952246; a=rsa-sha256; cv=none; b=SBDBX540KiQmSshaX2oBN6d+nI3AoBqac3jJhkXupXAnLmP8O0nhxKmAvhDM4iFX8CQ+5J uj40mJlYEjApXAPS6sUmKNul7fvarhbGoquRTZM2S/TDGe04T+D9CFGDGCKrRu+hLTlDGW l8udbJlGGqelvXNX4T7xPdO2T7xq0RQ= Received: from smtp.kernel.org (transwarp.subspace.kernel.org [100.75.92.58]) by dfw.source.kernel.org (Postfix) with ESMTP id 1173D5C0496; Thu, 7 Nov 2024 04:06:10 +0000 (UTC) Received: by smtp.kernel.org (Postfix) with ESMTPSA id 5A2F1C4CECC; Thu, 7 Nov 2024 04:06:54 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1730952414; bh=pIOR41q4cWEp5TvsSbu0pfsJtNNoU/okYdZg83G+Thc=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=pD7qkuYTeD8r4ABgbvv3a68w+27tX+NreylHr1psKlXA65COXvL/jX9wQTFLY5CJM jmhgNNqKA7dVgmU1F7otTbNf4ZpLJCzkdZcZw8+5WFrIw3oBLXATIPVofK7JSMS7Oz 2Z4y5/seEEBVY1uaGfNDGV36yMdEeucpGJo1pT5w= Date: Wed, 6 Nov 2024 20:06:53 -0800 From: Andrew Morton To: Yafang Shao Cc: willy@infradead.org, linux-mm@kvack.org Subject: Re: [PATCH] mm/readahead: Fix large folio support in async readahead Message-Id: <20241106200653.17640c022a94e0eec9276326@linux-foundation.org> In-Reply-To: References: <20241106092114.8408-1-laoar.shao@gmail.com> <20241106130318.91f05382d2c0bbd2be3abff5@linux-foundation.org> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit X-Rspamd-Server: rspam04 X-Rspamd-Queue-Id: B4822180005 X-Stat-Signature: 8yd5z3kgdejaka9x4rijrcwz7huscega X-Rspam-User: X-HE-Tag: 1730952390-620645 X-HE-Meta: U2FsdGVkX1+8tJmn5HR9yBwtfXEJWKbiR1iiCoZnyQ6Vl01MXK+lJC7fk+uwGBtGGdBVFzOeUCE4/9cxLw5QGJgYy4JjGLvou6osW4bbesbVK3WWn/TnOSE/Mhk9+6iBFoeY2J0xYh7NeLE9Xg7ZKVP/HxGuRCmIox6TJD7gkbtA9Q1caZ79URg8MypkfI/roYmyELWTDeVxaBr30y+grU2/eV5Zqc2V7BlaxgJOiW94quqZSvddojBTdbbp+nGcFu3WN5LR6nQ6veqPGl2BRomP37PFOa5TQkCX5sWUxMwvslBIk1I4jWGZ/sJgJQGA0OkWh9jtPMQaJIt3ceTy6nSv0USFdbXlxUjB7FO1HWPs1vSsPP/IfaEj7a1g/IbSo1q1lL/I4gabFyk9zjF1dr5YYBd+YNGlMe42mS9zqdxlCGSJd5w8MfPR1+gLlcyHYRAJtCKBfTraC5kc+T8fI8Gkz7C6iogxE3BWMC5N327Ihsa6gJhMBW4cjKrwWUuz1NzlLxvu5qq5MGmPjSuImhTDoL/vlhwownW0QjlICZ4EJR0PvTEsFp6KuvcdhUTuCA1Srp4wMBHMy1eM9LeatJoTZcwV/oguAxZz5A/7EvfV0vpLlJGCoZgPyfSlYYlvXry9yy7AauGGdW2XutiC1dFKoitS37kn0+/KLYOZ4I2XxlkxvRynC5hGvi1sO8FVZVfwXSw/uxPWm7g+GjPpEeOnBqEpLNDtbm8/dhQ69fGGnKP7WxnRAGh7cdRFgbRsFaQXF2fMPQb7FCvD9p5aWPrkvZ1ThJtD04I304Hf6rN9NSufaH0xpx7AGixHis99Tu9KcbeH9MOFi0i2gzdu3NSpoWHlcaA+CGyvjH0lEJip3QOuaaSA6JNCExLQFJhQVrH9a9clsiVRFmefBDdCE4jbJvoZyPy9P4b5ky6lPFVuTFztW4gxrE+RTAsJ9C8cbmguEHE8y+muWuQIYLL UrDA4H6M 51O8r0jb0fnosPr76uMtGSIzugeR/9J7+Ad1DL/uBSGXzz5OH+BhsAPKxFXvFJ9hZSKfqXikQAS5rh2Cq6WWEz6nRrYeUGhMGSBzedtLurBLNbn5CLWt3QFQCEZHNm90kIgW5Mu9sQ5TknSO611fphq468rjp9Rzilb0rUpJpqzbi80JyliQC+9H9cT6DAWk3lA7GYJxLBp/lWdOIpLBe+NyljxcV+0Cm5tW85XSjk2kOnn7Z/F3GNIByjejYaPsJ1B53ALnlkHY5k8JQff/StzrLaImgSK6gOv1A6aN/QccEvtL8hxiZgFp53hRFewKWCl9Oz9Jw3HIVbHtJ2w1dg3E1LtdxO+ECzG/5Ts9gj8HNsIG2oI+lU4kS10A+mjN4ncDBH6VEB0VNnp8= 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 Thu, 7 Nov 2024 11:39:36 +0800 Yafang Shao wrote: > On Thu, Nov 7, 2024 at 5:03 AM Andrew Morton wrote: > > > > On Wed, 6 Nov 2024 17:21:14 +0800 Yafang Shao wrote: > > > > > When large folio support is enabled and read_ahead_kb is set to a smaller > > > value, ra->size (4MB) may exceed the maximum allowed size (e.g., 128KB). To > > > address this, we need to add a conditional check for such cases. However, > > > this alone is insufficient, as users might set read_ahead_kb to a larger, > > > non-hugepage-aligned value (e.g., 4MB + 128KB). In these instances, it is > > > essential to explicitly align ra->size with the hugepage size. > > > > How much performance improvement is this likely to offer our users? > > The performance boost comes from enabling the use of hugepages > directly. Previously, users were unable to leverage large folios as > expected. With this change, however, large folios are now usable as > intended. Thanks, but I was hoping for something quantitative. Some nice before- and-after testing? How important/useful/impactful is this change? > This improvement addresses a critical need in services like AI > inference, which benefit substantially from hugetlbfs. However, using > hugetlbfs effectively within containerized environments can be > challenging. To overcome this limitation, we explored large folios as > a more flexible and production-friendly alternative. > > > IOW, should we consider backporting it? > > We should consider backporting this change. We've already backported > it to our local 6.1.y kernel, where it's performing well. > The Fixes tag should ensure it will be included in the stable kernel, right? For most subsystems, yes. In MM an explicit cc:stable is needed. Along with a changelog which permits readers to understand why a backport is proposed.