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 X-Spam-Level: X-Spam-Status: No, score=-0.8 required=3.0 tests=BAYES_00,DATE_IN_PAST_96_XX, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, USER_AGENT_SANE_2 autolearn=no autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 767F7C433FE for ; Sat, 5 Dec 2020 11:08:28 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 3CFF522D6F for ; Sat, 5 Dec 2020 11:08:28 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1729450AbgLELHh (ORCPT ); Sat, 5 Dec 2020 06:07:37 -0500 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:57784 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1729484AbgLELFE (ORCPT ); Sat, 5 Dec 2020 06:05:04 -0500 Received: from mail-ed1-x541.google.com (mail-ed1-x541.google.com [IPv6:2a00:1450:4864:20::541]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 7C524C061A55 for ; Sat, 5 Dec 2020 03:04:18 -0800 (PST) Received: by mail-ed1-x541.google.com with SMTP id b73so8518350edf.13 for ; Sat, 05 Dec 2020 03:04:18 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=from:message-id:subject:to:cc:in-reply-to:references:date :mime-version:content-transfer-encoding; bh=ptB7VjFOHXGa3Nl2TvXAUSYtLzguBp9ctPeePIRKIvM=; b=mjYNJ6wrOZ/8oP6erkxFQT5rWHE0geqzUr2wuhi57zBWlSf0GkHslQultnxdYadYPi qEZejANd1krMu6PmWcdBj9SN0R/2u1eP9ypxXDbvnBbSRTGcFQvpvp7UfdUdx6wIo/37 EpjPqgZbSmkqle5HyZo6fvSUTTJXhBhR5n6K29Yye2N2pRYukUGwDZTLytTd5SvRQEPA OQbVq4MAX3YoX5NtV+la9YiDKlU2Ca9LdCmjKRxgHnmpUpi/lXHqjGXS55ayZVXsxusd xWVfhTi+9Y8tY71fbJFG2iPnLVRRR8k5V+ZvaSsH3DnS4M5vsGXoCb8wqIjnQk8Rp9JK 2O2g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:message-id:subject:to:cc:in-reply-to :references:date:mime-version:content-transfer-encoding; bh=ptB7VjFOHXGa3Nl2TvXAUSYtLzguBp9ctPeePIRKIvM=; b=JQOuuy2imDgIfmdQHOaFKKKfQ35YVz5M512vonI4CqCWjBkNLsUi44Z5v6f25dRRXy 4ay8R+oO1jDHCoKCWC2dfFbJCCikRBKBS0qA2Cl4GgfDejr0QP8KU85DYWzPHrvBV90N BRz6dayzCDShztuVK9/SevcsZwxtVh9qRxE8/858vIl+RFtPxjLRojnJ8VMnwTL1WuRN IkgWI/o3HEooWJHCqJdI4h+aRMYIDkeyC5x6V/Gu5I8r673sFD1tln+5RJko7qwYEnup f96voWvvwgzRu29eFVKYH5yVGCdv7XvywpXkng/lFdyDAUmLswbJ40ULe3/ilzVRIuGq Kmxw== X-Gm-Message-State: AOAM531iko2WjlcgbfrCrZyn03eiRs/vcaRTD45V+5faBeUnc9IbyT/W X2cXefbEaNC1CiyZMKDV5Gc= X-Google-Smtp-Source: ABdhPJww6rtnhyZ6J5HO0cyBw7T7LcSslvTFiC1k1kUHZvqssKFJtXIpiRv9/asus/Ky1CQsJO+QtA== X-Received: by 2002:a50:ff0c:: with SMTP id a12mr11701689edu.79.1607166257309; Sat, 05 Dec 2020 03:04:17 -0800 (PST) Received: from ubuntu-laptop (ip5f5bfce9.dynamic.kabel-deutschland.de. [95.91.252.233]) by smtp.googlemail.com with ESMTPSA id n1sm4963181ejb.2.2020.12.05.03.04.15 (version=TLS1_2 cipher=ECDHE-ECDSA-CHACHA20-POLY1305 bits=256/256); Sat, 05 Dec 2020 03:04:16 -0800 (PST) From: Bean Huo X-Google-Original-From: Bean Huo Message-ID: Subject: Re: [PATCH RFC] mm: Let readahead submit larger batches of pages in case of ra->ra_pages == 0 To: Christoph Hellwig Cc: Andrew Morton , linux-mm@kvack.org, linux-kernel@vger.kernel.org, beanhuo@micron.com, Richard Weinberger In-Reply-To: <20200911094709.GB14158@infradead.org> References: <20200904144807.31810-1-huobean@gmail.com> <20200904110938.d9a2cb53a58e67a15c960f47@linux-foundation.org> <20200911094709.GB14158@infradead.org> Content-Type: text/plain; charset="UTF-8" Date: Fri, 11 Sep 2020 13:35:23 +0200 Mime-Version: 1.0 X-Mailer: Evolution 3.28.5-0ubuntu0.18.04.2 Content-Transfer-Encoding: 7bit Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, 2020-09-11 at 10:47 +0100, Christoph Hellwig wrote: > > Hi Andrew > > Sorry, I am still not quite understanding your above three > > questions. > > > > Based on my shallow understanding, ra_pages is associated with > > read_ahead_kb. Seems ra_pages controls the maximum read-ahead > > window > > size, but it doesn't work when the requested size exceeds > > ra_pages. > > > > If I set the read_ahead_kb to 0, also, as Christoph mentioned, MTD > > forcibly sets ra_pages to 0. I think the intention is that only > > wants > > to disable read-ahead, however, doesn't want > > generic_file_buffered_read() to split the request and read data > > with > > 4KB chunk size separately. > > They way I understood Richard this is intentional. Hi Christoph Thanks. understood now, MTD expects this result. Even so, I think this patch doesn't impact MTD because the flash-based FS only achieved the readpage. Inside __do_page_cache_readahead will use mapping->a_ops- >readpage to read data. Thanks, Bean