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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,FSL_HELO_FAKE,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 66AC9C3B186 for ; Tue, 11 Feb 2020 04:25:43 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 4139E206D7 for ; Tue, 11 Feb 2020 04:25:43 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=default; t=1581395143; bh=3QMBxcD7fDbKTeP+bFi3ghcNsyrvYeoitAhcCrdVhL0=; h=Date:From:To:Cc:Subject:References:In-Reply-To:List-ID:From; b=wmewKuqFPt4DtGtfyySvfylCAKmrC2vB42MOetYWjXzNu0kRJdLkV1i3njOmwJgY5 g2aLCYko5H7wEHO5X0qrnF+QpsOEFBQLKgXGB3Sz4Tna5qNQ9cfeyd+AisDIfSIqgS z6VL2y7+MDK0cWlMRquMUGtGRcZWLBkX8H9jZdVM= Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1728147AbgBKEZm (ORCPT ); Mon, 10 Feb 2020 23:25:42 -0500 Received: from mail-pl1-f193.google.com ([209.85.214.193]:36515 "EHLO mail-pl1-f193.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727481AbgBKEZl (ORCPT ); Mon, 10 Feb 2020 23:25:41 -0500 Received: by mail-pl1-f193.google.com with SMTP id a6so3718947plm.3 for ; Mon, 10 Feb 2020 20:25:40 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=V9KO1k9P8J3nM1/EjQwGBTH9H+54xdTL4UiNZzfIiIA=; b=LDfCTC/a9lACRyt/I8wPrZgYqbnFBRGBC5bGiEZv10ocg2VsnYAr/7t/zbq+YwiAle xPrpWdEcKjufQEEVPSNMwdgqXPCt9h3S1gFC7Rcjs7rT68Fi+uv1XwuowH2lTQPWQX3J bCSOpoaxOwtvKXSTQ51u526lKJIK0yxRPnduJzb+SlZX0dbLQCVyn7SXXdlmnxeDetLK 9tiDXrKwPxX2gA2VGfnTQfNLupM7uerPtbOQePIlF6d+S1XnL9aV3U6K4iDC5Yz1Hawu NRc+GoPxqFIndLVJe5E9HuoYCphp7G/N8Vyfd4lGitbbf5V4u6X1nsFzCavInLlp2irW fI8g== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to:user-agent; bh=V9KO1k9P8J3nM1/EjQwGBTH9H+54xdTL4UiNZzfIiIA=; b=CLC2DERIVvR2XHLvmVGMSoYDv8JJnpvqs0hxV1t0jCuF9WEzhyoD/EYP/0rTdUb4xU VoKY+mBELsPUE65GUcQ496Cut7hrV2gFshhZPcRKoxi5Z6LhusN/py5GTYCXpKj0Tasg YQ+tHJdb+CBCr+M+RwFmu5Z9hORjcoxzy9xqb/9N1QcitfQP+MKBdfXVSGpXDU/8Kykm M7wX8bppLcN6qgAeuCeCTwEMNMzyrX5PcOxcIyTNYWWbqQQVI50bx84svRUQfuoMTndf pCqKdaK8wYGTC32fLM6x1dorZwEYOkx7YZlBQ0QMOL7vXMLnj4Eam2fNCHYL8eY2tg7u WLbw== X-Gm-Message-State: APjAAAXqsRoub2SIBparc+mSm7PlewbXgNNiaXDFS2g6jKZHxHAv5srK xBaMtaYO3Rf6BJOrWREiiifgBHmG X-Google-Smtp-Source: APXvYqxJp2Ga/NJR5Trp9Ws/QTu3Tgarvy4sJ1sGXdurS3XAnPql3Ks1sGNlySgCG+34o82mwQ7xcg== X-Received: by 2002:a17:902:61:: with SMTP id 88mr1341669pla.17.1581395139532; Mon, 10 Feb 2020 20:25:39 -0800 (PST) Received: from google.com ([2620:15c:211:1:3e01:2939:5992:52da]) by smtp.gmail.com with ESMTPSA id z10sm1639684pgz.88.2020.02.10.20.25.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 10 Feb 2020 20:25:38 -0800 (PST) Date: Mon, 10 Feb 2020 20:25:36 -0800 From: Minchan Kim To: Matthew Wilcox Cc: Andrew Morton , linux-mm , Josef Bacik , Johannes Weiner , Jan Kara , LKML Subject: Re: [PATCH] mm: fix long time stall from mm_populate Message-ID: <20200211042536.GB242563@google.com> References: <20200211001958.170261-1-minchan@kernel.org> <20200211011021.GP8731@bombadil.infradead.org> <20200211035004.GA242563@google.com> <20200211035412.GR8731@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200211035412.GR8731@bombadil.infradead.org> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Feb 10, 2020 at 07:54:12PM -0800, Matthew Wilcox wrote: > On Mon, Feb 10, 2020 at 07:50:04PM -0800, Minchan Kim wrote: > > On Mon, Feb 10, 2020 at 05:10:21PM -0800, Matthew Wilcox wrote: > > > On Mon, Feb 10, 2020 at 04:19:58PM -0800, Minchan Kim wrote: > > > > filemap_fault > > > > find a page form page(PG_uptodate|PG_readahead|PG_writeback) > > > > > > Uh ... That shouldn't be possible. > > > > Please see shrink_page_list. Vmscan uses PG_reclaim to accelerate > > page reclaim when the writeback is done so the page will have both > > flags at the same time and the PG reclaim could be regarded as > > PG_readahead in fault conext. > > What part of fault context can make that mistake? The snippet I quoted > below is from page_cache_async_readahead() where it will clearly not > make that mistake. There's a lot of code here; please don't presume I > know all the areas you're talking about. Sorry about being not clear. I am saying filemap_fault -> do_async_mmap_readahead Let's assume the page is hit in page cache and vmf->flags is !FAULT_FLAG TRIED so it calls do_async_mmap_readahead. Since the page has PG_reclaim and PG_writeback by shrink_page_list, it goes to do_async_mmap_readahead if (PageReadahead(page)) fpin = maybe_unlock_mmap_for_io(); page_cache_async_readahead if (PageWriteback(page)) return; ClearPageReadahead(page); <- doesn't reach here until the writeback is clear So, mm_populate will repeat the loop until the writeback is done. It's my just theory but didn't comfirm it by the testing. If I miss something clear, let me know it. Thanks! > > > > > > > /* > > > * Same bit is used for PG_readahead and PG_reclaim. > > > */ > > > if (PageWriteback(page)) > > > return; > > > > > > ClearPageReadahead(page);