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=-2.1 required=3.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,T_DKIM_INVALID, USER_AGENT_MUTT autolearn=ham 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 C2AF1ECDFB3 for ; Mon, 16 Jul 2018 12:41:33 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 7B37F2084E for ; Mon, 16 Jul 2018 12:41:33 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="U+dn8b5v" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 7B37F2084E Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1730310AbeGPNIr (ORCPT ); Mon, 16 Jul 2018 09:08:47 -0400 Received: from bombadil.infradead.org ([198.137.202.133]:53212 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1728524AbeGPNIr (ORCPT ); Mon, 16 Jul 2018 09:08:47 -0400 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.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:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=zPEqDOFprwoXXn63mjwk15X67uYxvwTZxSf1rrlNs6M=; b=U+dn8b5vlK1cX8FCLp89UNn4R IT1AyYuys9JF/h9mNac33UahDPjqSFWLtzgaIgoP+ONNNOHEL/yqsgMqnvrBb/XsR6YAUSc4MG7b8 NJ1I0yxOawJy4qIf7fP/QvVie/Ub3GhiscQEjE/VbeQaZMKJQS543fyYn1iay3B/DBQ2TRm9tvjhv NXXo0XGf7ZvD2d5XST2nJLQWqQkm9BowyWE4TN/NUdIIFNpx8CH/nULl+cYBk8m2Kod3K6guoTRf6 7kiucijhA04b68KUVg/yYJjcaHoVMewJShkboMxqNPJ+hhjvEMqG0ziejIEw8TbfhVgRGT20NEai3 L2RYSeisQ==; Received: from willy by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1ff2oV-0006nN-Pe; Mon, 16 Jul 2018 12:41:15 +0000 Date: Mon, 16 Jul 2018 05:41:15 -0700 From: Matthew Wilcox To: Michal Hocko Cc: Dave Chinner , James Bottomley , Linus Torvalds , Waiman Long , Al Viro , Jonathan Corbet , "Luis R. Rodriguez" , Kees Cook , Linux Kernel Mailing List , linux-fsdevel , linux-mm , "open list:DOCUMENTATION" , Jan Kara , Paul McKenney , Andrew Morton , Ingo Molnar , Miklos Szeredi , Larry Woodman , "Wangkai (Kevin,C)" Subject: Re: [PATCH v6 0/7] fs/dcache: Track & limit # of negative dentries Message-ID: <20180716124115.GA7072@bombadil.infradead.org> References: <18c5cbfe-403b-bb2b-1d11-19d324ec6234@redhat.com> <1531336913.3260.18.camel@HansenPartnership.com> <4d49a270-23c9-529f-f544-65508b6b53cc@redhat.com> <1531411494.18255.6.camel@HansenPartnership.com> <20180712164932.GA3475@bombadil.infradead.org> <1531416080.18255.8.camel@HansenPartnership.com> <1531425435.18255.17.camel@HansenPartnership.com> <20180713003614.GW2234@dastard> <20180716090901.GG17280@dhcp22.suse.cz> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180716090901.GG17280@dhcp22.suse.cz> User-Agent: Mutt/1.9.2 (2017-12-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jul 16, 2018 at 11:09:01AM +0200, Michal Hocko wrote: > On Fri 13-07-18 10:36:14, Dave Chinner wrote: > [...] > > By limiting the number of negative dentries in this case, internal > > slab fragmentation is reduced such that reclaim cost never gets out > > of control. While it appears to "fix" the symptoms, it doesn't > > address the underlying problem. It is a partial solution at best but > > at worst it's another opaque knob that nobody knows how or when to > > tune. > > Would it help to put all the negative dentries into its own slab cache? Maybe the dcache should be more sensitive to its own needs. In __d_alloc, it could check whether there are a high proportion of negative dentries and start recycling some existing negative dentries.