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=-9.9 required=3.0 tests=DKIMWL_WL_MED,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,USER_AGENT_SANE_1,USER_IN_DEF_DKIM_WL 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 B5A49C433DF for ; Wed, 3 Jun 2020 22:20:02 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 919E3207D3 for ; Wed, 3 Jun 2020 22:20:02 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=google.com header.i=@google.com header.b="q2j+NT0e" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726844AbgFCWUB (ORCPT ); Wed, 3 Jun 2020 18:20:01 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:44490 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726354AbgFCWUA (ORCPT ); Wed, 3 Jun 2020 18:20:00 -0400 Received: from mail-qk1-x743.google.com (mail-qk1-x743.google.com [IPv6:2607:f8b0:4864:20::743]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id A7B7EC08C5C0 for ; Wed, 3 Jun 2020 15:20:00 -0700 (PDT) Received: by mail-qk1-x743.google.com with SMTP id c14so3974075qka.11 for ; Wed, 03 Jun 2020 15:20:00 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=google.com; s=20161025; h=date:from:to:cc:subject:in-reply-to:message-id:references :user-agent:mime-version; bh=u8bt+zJqcOzYuwXNEkBi3TSw8qIySQwkMwxxZhfbW18=; b=q2j+NT0eKKrPZcaZj7zOdpJf6VRJKe1lfRidzOhPqGQQMYv9LP6cbgWlNpGtOAYYYo 1F8XkS4JBGT45vJQcJQiseFEIZiJsyHIUcmahuuHUvUbA/O3i1sn2RFFPH0LAOu338Lq GZL7uPZ8PPfpOlH9nV2nXPeChGR8mwkfvRcICVF30rJQkLPmMZV+7KLUbHHd98jItvaK aAEfNVpnz2AjS8AUxcd5vS9qSXZk8xJvlC7cOMaR3PuBj35OXO76ZIH1K/aUrhfv5XEn pdTzFxFZs9KXENZRy5YgVfW5jMX61cOnTsCK/Q9xLc7aqEhNi2vQ3DahE9d+fAVSefdf tlpg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:in-reply-to:message-id :references:user-agent:mime-version; bh=u8bt+zJqcOzYuwXNEkBi3TSw8qIySQwkMwxxZhfbW18=; b=hYhoSWhLkudNpkoOdN7opWpY8pkvDOIL6YYO8pi5NqMy5V9WIPyy0EGOCXRs6WT+/G xuZKj8s8qJqF4ltGS6Ezamv8jkTNDkVO8ITGsn+wmmsfCVid0lW3HGOd54vbHBJfDurk SVCZoFjjgeMdH56HcY87ID6+h7NFE3c1XZPJObsixaCjPlS5CZUsmylLKoZ+BkgC4GOA Z7q3e6kWlp6L6pn77NWiL2v4uVo/0fOu3JfuEHFXQI2AvG8BhXi8Wvk/ntcKByFpcEAV jOIrNnf+j85Rle0JQ81x18JpP3sEIW4RlcgPZkCVvKgfakRB7Ayc8mDTAS/wN1pUTSQT XhbQ== X-Gm-Message-State: AOAM531+qj9lB21Whx7J/2HldlIuR8WDVcu7Os8f4y8DDqyT0vfHKxXJ wpUGVhVqrQa1vC6qVYqYi4z3Mg== X-Google-Smtp-Source: ABdhPJw05gsQ6aNcDdc1C5CE24VGVGWfuS8FT1e1NBeJHtJHf+z9mkEvKoPt0qQbf38jhzBbMLSP7g== X-Received: by 2002:a37:9586:: with SMTP id x128mr1874208qkd.312.1591222799472; Wed, 03 Jun 2020 15:19:59 -0700 (PDT) Received: from eggly.attlocal.net (172-10-233-147.lightspeed.sntcca.sbcglobal.net. [172.10.233.147]) by smtp.gmail.com with ESMTPSA id h50sm3328294qte.25.2020.06.03.15.19.56 (version=TLS1 cipher=ECDHE-ECDSA-AES128-SHA bits=128/128); Wed, 03 Jun 2020 15:19:58 -0700 (PDT) Date: Wed, 3 Jun 2020 15:19:42 -0700 (PDT) From: Hugh Dickins X-X-Sender: hugh@eggly.anvils To: Matthew Wilcox cc: Hugh Dickins , Johannes Weiner , Andrew Morton , Song Liu , "Kirill A. Shutemov" , linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] mm,thp: stop leaking unreleased file pages In-Reply-To: <20200603215122.GR19604@bombadil.infradead.org> Message-ID: References: <20200526160140.GC850116@cmpxchg.org> <20200603215122.GR19604@bombadil.infradead.org> User-Agent: Alpine 2.11 (LSU 23 2013-08-11) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Wed, 3 Jun 2020, Matthew Wilcox wrote: > On Wed, May 27, 2020 at 02:28:10PM -0700, Hugh Dickins wrote: > > Saying "source inspection" reminds me: there is another funny in there, > > but I don't think it matters very much in practice, and might need > > rather a lot of testing to justify any particular patch: where > > page_cache_sync_readahead() asks for PAGE_SIZE pages! > > > > "end - index" seems a more reasonable number to me: but then we > > might find that reading ahead into the next huge extent had actually > > been a useful optimization (and those readahead functions impose > > their own caps, so PAGE_SIZE shouldn't work out too outrageously). > > That readahead was only added in 99cb0dbd47a15d395bf3faa78dc122bc5efe3fc0 > so it probably hasn't really been performance tested yet. I can well imagine that an entirely new body of code, exercised in the background by khugepaged, will not be a leading candidate for performance comparisons - rightly so; but arguing that by the commit being in the tree for only eight months seems... odd :) Hugh