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=-3.6 required=3.0 tests=BAYES_00,DKIM_INVALID, DKIM_SIGNED,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS 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 DE174C433DB for ; Mon, 15 Mar 2021 23:46:57 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 10C5164DE7 for ; Mon, 15 Mar 2021 23:46:57 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 10C5164DE7 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=owner-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix) id 840BD6B0036; Mon, 15 Mar 2021 19:46:56 -0400 (EDT) Received: by kanga.kvack.org (Postfix, from userid 40) id 7F0F56B006C; Mon, 15 Mar 2021 19:46:56 -0400 (EDT) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 66B716B0070; Mon, 15 Mar 2021 19:46:56 -0400 (EDT) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0133.hostedemail.com [216.40.44.133]) by kanga.kvack.org (Postfix) with ESMTP id 494F36B0036 for ; Mon, 15 Mar 2021 19:46:56 -0400 (EDT) Received: from smtpin26.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay03.hostedemail.com (Postfix) with ESMTP id E53A98249980 for ; Mon, 15 Mar 2021 23:46:55 +0000 (UTC) X-FDA: 77923746390.26.CC36B61 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf18.hostedemail.com (Postfix) with ESMTP id 05BC52000F50 for ; Mon, 15 Mar 2021 23:46:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=casper.20170209; h=In-Reply-To:Content-Type:MIME-Version: References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=q5WpvI+u/n7oGrB8MBjwp1b76X1ojPJiu1UvApa7aOM=; b=XxzZQEuiUGYF4WLGRYxkb+VC/J j2qyAgXjLSZg41dJFHIn5P1zKih5kQD/1ZWStdzhurTmzSKPCZXVdFVNomLX981LgUT0SdsO7MGmc mHErX73nV1kJErajGuK4dlSwT9B0AG/+qDmdfmbDFDLZNuZUllC3fzXFl2qRSPI5rKFsGF7tzp2j4 VpLciNIv8K9JQLZT+skTA/JZav74HyRhK08CR2QiLlyYFypv2NSAwihXfevIVKNIUUqMerD82/bJV mjBn1kT+ta3yOrvCQiSu6wVpJkYUGl2T2NgIy+2mg62oIPjtP2VJV3LetXC2cWeNp5/iKX/7H6eyu 3bAXjf1w==; Received: from willy by casper.infradead.org with local (Exim 4.94 #2 (Red Hat Linux)) id 1lLwuT-0012sM-9J; Mon, 15 Mar 2021 23:46:24 +0000 Date: Mon, 15 Mar 2021 23:46:05 +0000 From: Matthew Wilcox To: Andrew Morton Cc: Chris Goldsworthy , Alexander Viro , linux-mm@kvack.org, linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org, Laura Abbott Subject: Re: [PATCH v3] fs/buffer.c: Revoke LRU when trying to drop buffers Message-ID: <20210315234605.GD2577561@casper.infradead.org> References: <2f13c006ad12b047e9e4d5de008e5d5c41322754.1610572007.git.cgoldswo@codeaurora.org> <20210315164138.c15727adeb184313f5e7e9f6@linux-foundation.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20210315164138.c15727adeb184313f5e7e9f6@linux-foundation.org> X-Stat-Signature: ccanabxq5m99rxmwmkac1mx84uh56quc X-Rspamd-Server: rspam05 X-Rspamd-Queue-Id: 05BC52000F50 Received-SPF: none (infradead.org>: No applicable sender policy available) receiver=imf18; identity=mailfrom; envelope-from=""; helo=casper.infradead.org; client-ip=90.155.50.34 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1615852005-87994 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 Mon, Mar 15, 2021 at 04:41:38PM -0700, Andrew Morton wrote: > > When a buffer is added to the LRU list, a reference is taken which is > > not dropped until the buffer is evicted from the LRU list. This is the > > correct behavior, however this LRU reference will prevent the buffer > > from being dropped. This means that the buffer can't actually be dropped > > until it is selected for eviction. There's no bound on the time spent > > on the LRU list, which means that the buffer may be undroppable for > > very long periods of time. Given that migration involves dropping > > buffers, the associated page is now unmigratible for long periods of > > time as well. CMA relies on being able to migrate a specific range > > of pages, so these types of failures make CMA significantly > > less reliable, especially under high filesystem usage. > > It looks like patch this turns drop_buffers() into a very expensive > operation. And that expensive operation occurs under the > address_space-wide private_lock, which is more ouch. This patch set is obsoleted by Minchan Kim's more recent patch-set.