From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.1 (2015-04-28) on archive.lwn.net X-Spam-Level: X-Spam-Status: No, score=-5.6 required=5.0 tests=DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,RCVD_IN_DNSWL_HI, T_DKIM_INVALID,T_TVD_MIME_EPI autolearn=ham autolearn_force=no version=3.4.1 Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by archive.lwn.net (Postfix) with ESMTP id 20BCF7DF81 for ; Thu, 12 Jul 2018 18:06:36 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1727714AbeGLSRA (ORCPT ); Thu, 12 Jul 2018 14:17:00 -0400 Received: from mail-it0-f68.google.com ([209.85.214.68]:54842 "EHLO mail-it0-f68.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732208AbeGLSQ7 (ORCPT ); Thu, 12 Jul 2018 14:16:59 -0400 Received: by mail-it0-f68.google.com with SMTP id s7-v6so8063801itb.4; Thu, 12 Jul 2018 11:06:19 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux-foundation.org; s=google; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=gH/7xbbvaNGX9vSnYeWTYXoV+8anNYt8k/9JV13LWrA=; b=aP3OnuFxtS8gQffe2pC3eqiZ7z0eItch81qDVpZjg9/UPfW9K2D3O/sfV0ezG0v1oW udfMJQfxoVRcASmTyJSkk0Eq5kamfClANPjGXyxnlvMpECwZuT1H9FmkrJhvRgc1Wxuj Qc9lnyN7u3B6T/pZ/pg/fLlO41M63sDiZabW4= 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=gH/7xbbvaNGX9vSnYeWTYXoV+8anNYt8k/9JV13LWrA=; b=pilxRdtSiFbU+2o25PmRlaqOOzJsf27Sl4dEPnRgCjvO9k4N5aPHZEfx59sg2bpoBv TWZoyIfnLm4hB4OhAew/9NciUKDLN1YI9kugJz3oXIKN/iaQdhwgtGm9YAXOcuqKiRe3 g0rWWm+oeaXIHy0VSAUYueCwu13R2D2SMIny73GeGALYVdY1QIMtKIlGLZYzijhvJX5J c3eLXpFX0dQXUd/GgoYMdwQmouPmQdpxbC7Bo+WdO6YYqsXGCG7+9WOaB44nQhgAfKUN OENxSmfdi2+8p52Z57qV0RQRYoagqZ8uH6Ss+vi7ntLNB5N9a6xWw0HEkTm/rINW6o7f V1dA== X-Gm-Message-State: AOUpUlGAZ/uzPeEAAadHs0Sp+MtWOytU5FcOdL3tXCOt4L4C4P8AYB8c 38enULhEAT9YoCMD0dfODAzp59LwIrxVKZXNxXU= X-Google-Smtp-Source: AAOMgpdBH3YGZAwkCx//upzHm4xPP9SGLrSwDEqDNieXZkPsWYnGUwXqVfAo0RXv6XPlj+UxbaXyckLKc3Snc13fKGs= X-Received: by 2002:a24:5002:: with SMTP id m2-v6mr2172832itb.16.1531418779203; Thu, 12 Jul 2018 11:06:19 -0700 (PDT) MIME-Version: 1.0 References: <62275711-e01d-7dbe-06f1-bf094b618195@redhat.com> <20180710142740.GQ14284@dhcp22.suse.cz> <20180711102139.GG20050@dhcp22.suse.cz> <9f24c043-1fca-ee86-d609-873a7a8f7a64@redhat.com> <1531330947.3260.13.camel@HansenPartnership.com> <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> In-Reply-To: <1531416080.18255.8.camel@HansenPartnership.com> From: Linus Torvalds Date: Thu, 12 Jul 2018 11:06:08 -0700 Message-ID: Subject: Re: [PATCH v6 0/7] fs/dcache: Track & limit # of negative dentries To: James Bottomley Cc: Matthew Wilcox , Waiman Long , Michal Hocko , 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)" Content-Type: multipart/mixed; boundary="00000000000056798e0570d138d2" Sender: linux-doc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org --00000000000056798e0570d138d2 Content-Type: text/plain; charset="UTF-8" On Thu, Jul 12, 2018 at 10:21 AM James Bottomley wrote: > > On Thu, 2018-07-12 at 09:49 -0700, Matthew Wilcox wrote: > > > > I don't know that it does work. Or that it works well. > > I'm not claiming the general heuristics are perfect (in fact I know we > still have a lot of problems with dirty reclaim and writeback). I think this whole "this is about running out of memory" approach is wrong. We *should* handle that well. Or well enough in practice, at least. Do we? Maybe not. Should the dcache be the one area to be policed and worked around? Probably not. But there may be other reasons to just limit negative dentries. What does the attached program do to people? It's written to be intentionally annoying to the dcache. 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