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=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS, URIBL_BLOCKED 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 D9B93CA9EA0 for ; Fri, 18 Oct 2019 21:03:09 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 9A4C320869 for ; Fri, 18 Oct 2019 21:03:09 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="YJ4zJBnO" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9A4C320869 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=gmail.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 3BF6E8E0005; Fri, 18 Oct 2019 17:03:09 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 370308E0003; Fri, 18 Oct 2019 17:03:09 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 285D38E0005; Fri, 18 Oct 2019 17:03:09 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0222.hostedemail.com [216.40.44.222]) by kanga.kvack.org (Postfix) with ESMTP id 08AC58E0003 for ; Fri, 18 Oct 2019 17:03:09 -0400 (EDT) Received: from smtpin22.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with SMTP id 660F69085 for ; Fri, 18 Oct 2019 21:03:08 +0000 (UTC) X-FDA: 76058130456.22.team20_558e48bd3b60c X-HE-Tag: team20_558e48bd3b60c X-Filterd-Recvd-Size: 4511 Received: from mail-qk1-f196.google.com (mail-qk1-f196.google.com [209.85.222.196]) by imf07.hostedemail.com (Postfix) with ESMTP for ; Fri, 18 Oct 2019 21:03:07 +0000 (UTC) Received: by mail-qk1-f196.google.com with SMTP id p4so6629181qkf.5 for ; Fri, 18 Oct 2019 14:03:07 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=w5yfTzlXuD4kav5HMjCh3XSfoZZpoehtbD9nhzYMyUM=; b=YJ4zJBnOuYfs3IkYqza76LtzacYPjLmzE1cNIVUWPWz2I0HHMP/AG1snDhBdxcndda qw5EzeWr8ANzVlfsn4a6eOjVa8PDZiQ4pdtSBDZ7qnt/hetcMXUycIb4e/VSfwEvdTSr Yf1EDMGPNUeE96tDTbvbaSXACVbmO+TavnO9M/+y3Q14jTIq5aHb3nNobu3YsFZ60o75 KX5/tzztz2ov7+K0HXdIj1X7c/dPlSqFZujA4aixVjzeRdnSIKNult7EpppnRmVq3aNC crCQlHQgq7GW/+SbgcqiOas9Hnwg4rluV7KDaBTV6mr5QUMCXkA0UG7o0nu4NEAiAipB Rrxg== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=w5yfTzlXuD4kav5HMjCh3XSfoZZpoehtbD9nhzYMyUM=; b=DSqap1o+w5z8NaEuMPlBddJnoGC/GHKUv//cQOB8i1uCprADtPU2UJhZYK0DFBtjEC FrVKUZQU+6Bm5+yzWRgkCSAuCHVORxn+uFvgBjhpz/rmsE8k71Z+tjkFlrYseYcNOq8H vEFreBwo2TBRaSbP7aG5eG3AsqM+S/miGY/6ch4C9Tq9YC3i7SVaziGSN765Tb6j3Vdd cXGMWH7Cv8IFCMIeUiBsvJdZ7xQasR8DWYAsQqxVllzTCLKJniGb/wb9hjvz/YUZbzYI ObpgFqixM3z3c3n68KYHtV9ooDXw+7d1ZzMLXpCBFk2TSM+SRqeSJTpXQdnSgy7clLeP l81w== X-Gm-Message-State: APjAAAWjP+JCBSG1kY29JXN0LdUJTm6yrOgQ5ESD26MHe95Ug6L9BB4I 7o1H6xpxPlplBvHNvCkKtL/RSvMeAvz2/0gFkUM= X-Google-Smtp-Source: APXvYqw8tNu0ZEcr9cUYkJv8QaKxcGJGz7c1mQDdMa03FSxMEnvUroWtRP1aKSvz4MkVzAn/r0dtQ+UUPuHmHpj4J9c= X-Received: by 2002:a05:620a:242:: with SMTP id q2mr10896151qkn.87.1571432587081; Fri, 18 Oct 2019 14:03:07 -0700 (PDT) MIME-Version: 1.0 References: <20191016221148.F9CCD155@viggo.jf.intel.com> <20191016221152.BF2171A3@viggo.jf.intel.com> <6ab6ca82-71d4-bdea-ae95-e0bebb5e71df@intel.com> In-Reply-To: <6ab6ca82-71d4-bdea-ae95-e0bebb5e71df@intel.com> From: Yang Shi Date: Fri, 18 Oct 2019 14:02:54 -0700 Message-ID: Subject: Re: [PATCH 3/4] mm/vmscan: Attempt to migrate page in lieu of discard To: Dave Hansen Cc: Dave Hansen , Linux Kernel Mailing List , Linux MM , Dan Williams , Keith Busch Content-Type: text/plain; charset="UTF-8" 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: On Fri, Oct 18, 2019 at 11:15 AM Dave Hansen wrote: > > On 10/17/19 10:30 AM, Yang Shi wrote: > >> + if (!PageHuge(page)) { > >> + int rc = migrate_demote_mapping(page); > >> + > >> + /* > >> + * -ENOMEM on a THP may indicate either migration is > >> + * unsupported or there was not enough contiguous > >> + * space. Split the THP into base pages and retry the > >> + * head immediately. The tail pages will be considered > >> + * individually within the current loop's page list. > >> + */ > >> + if (rc == -ENOMEM && PageTransHuge(page) && > >> + !split_huge_page_to_list(page, page_list)) > >> + rc = migrate_demote_mapping(page); > > I recalled when Keith posted the patch at the first time, I raised > > question about why not just migrating THP in a whole? The > > migrate_pages() could handle this. If it fails, it just fallbacks to > > base page. > > There's a pair of migrate_demote_mapping()s in there. I expected that > the first will migrate the whole THP and the second plus the split is > only used if fails the whole migration. Ah, that's right. I mis-read the first migrate_demote_mapping(). But, why calling migrate_demote_mapping() twice for THP and base page (if THP is failed) instead of calling migrate_pages() that does deal with all the cases. > > Am I reading it wrong?