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=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED 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 66CC1C3279B for ; Tue, 3 Jul 2018 01:11:41 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 20FAB23E6C for ; Tue, 3 Jul 2018 01:11:41 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 20FAB23E6C Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com 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 S1753574AbeGCBLi (ORCPT ); Mon, 2 Jul 2018 21:11:38 -0400 Received: from mx3-rdu2.redhat.com ([66.187.233.73]:45854 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1752636AbeGCBLg (ORCPT ); Mon, 2 Jul 2018 21:11:36 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.rdu2.redhat.com [10.11.54.6]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id F14824021FC2; Tue, 3 Jul 2018 01:11:35 +0000 (UTC) Received: from llong.remote.csb (ovpn-116-30.sin2.redhat.com [10.67.116.30]) by smtp.corp.redhat.com (Postfix) with ESMTP id 4B3A82166BA9; Tue, 3 Jul 2018 01:11:29 +0000 (UTC) Subject: Re: [PATCH v5 0/6] fs/dcache: Track & limit # of negative dentries To: Andrew Morton , Linus Torvalds Cc: Al Viro , Linux Kernel Mailing List , linux-fsdevel , Jan Kara , Paul McKenney , Ingo Molnar , Miklos Szeredi , Matthew Wilcox , Larry Woodman , James Bottomley , "Wangkai (Kevin,C)" , linux-mm@kvack.org, Michal Hocko References: <1530510723-24814-1-git-send-email-longman@redhat.com> <20180702141811.ef027fd7d8087b7fb2ba0cce@linux-foundation.org> From: Waiman Long Organization: Red Hat Message-ID: <1561585c-7d4d-da4a-e9f9-948198eaa562@redhat.com> Date: Tue, 3 Jul 2018 09:11:28 +0800 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:52.0) Gecko/20100101 Thunderbird/52.2.0 MIME-Version: 1.0 In-Reply-To: <20180702141811.ef027fd7d8087b7fb2ba0cce@linux-foundation.org> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit Content-Language: en-US X-Scanned-By: MIMEDefang 2.78 on 10.11.54.6 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.7]); Tue, 03 Jul 2018 01:11:36 +0000 (UTC) X-Greylist: inspected by milter-greylist-4.5.16 (mx1.redhat.com [10.11.55.7]); Tue, 03 Jul 2018 01:11:36 +0000 (UTC) for IP:'10.11.54.6' DOMAIN:'int-mx06.intmail.prod.int.rdu2.redhat.com' HELO:'smtp.corp.redhat.com' FROM:'longman@redhat.com' RCPT:'' Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/03/2018 05:18 AM, Andrew Morton wrote: > On Mon, 2 Jul 2018 12:34:00 -0700 Linus Torvalds wrote: > >> On Sun, Jul 1, 2018 at 10:52 PM Waiman Long wrote: >>> A rogue application can potentially create a large number of negative >>> dentries in the system consuming most of the memory available if it >>> is not under the direct control of a memory controller that enforce >>> kernel memory limit. >> I certainly don't mind the patch series, but I would like it to be >> accompanied with some actual example numbers, just to make it all a >> bit more concrete. >> >> Maybe even performance numbers showing "look, I've filled the dentry >> lists with nasty negative dentries, now it's all slower because we >> walk those less interesting entries". >> > (Please cc linux-mm@kvack.org on this work) > > Yup. The description of the user-visible impact of current behavior is > far too vague. > > In the [5/6] changelog it is mentioned that a large number of -ve > dentries can lead to oom-killings. This sounds bad - -ve dentries > should be trivially reclaimable and we shouldn't be oom-killing in such > a situation. The OOM situation was observed in an older distro kernel. It may not be the case with the upstream kernel. I will double check that. Cheers, Longman