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=-5.8 required=3.0 tests=BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,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 A54BCC433E0 for ; Mon, 15 Mar 2021 23:47:50 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 72E5464F5E for ; Mon, 15 Mar 2021 23:47:50 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233992AbhCOXrS (ORCPT ); Mon, 15 Mar 2021 19:47:18 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:59282 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S229524AbhCOXq5 (ORCPT ); Mon, 15 Mar 2021 19:46:57 -0400 Received: from casper.infradead.org (casper.infradead.org [IPv6:2001:8b0:10b:1236::1]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 3228AC06174A; Mon, 15 Mar 2021 16:46:57 -0700 (PDT) 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> Precedence: bulk List-ID: X-Mailing-List: linux-fsdevel@vger.kernel.org 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.