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 26E9FC4361B for ; Sun, 20 Dec 2020 19:29:37 +0000 (UTC) Received: from kanga.kvack.org (kanga.kvack.org [205.233.56.17]) by mail.kernel.org (Postfix) with ESMTP id 72DBA22C9C for ; Sun, 20 Dec 2020 19:29:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 72DBA22C9C 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 3794B6B005C; Sun, 20 Dec 2020 14:29:35 -0500 (EST) Received: by kanga.kvack.org (Postfix, from userid 40) id 329E46B005D; Sun, 20 Dec 2020 14:29:35 -0500 (EST) X-Delivered-To: int-list-linux-mm@kvack.org Received: by kanga.kvack.org (Postfix, from userid 63042) id 23EC36B0068; Sun, 20 Dec 2020 14:29:35 -0500 (EST) X-Delivered-To: linux-mm@kvack.org Received: from forelay.hostedemail.com (smtprelay0180.hostedemail.com [216.40.44.180]) by kanga.kvack.org (Postfix) with ESMTP id 0469D6B005C for ; Sun, 20 Dec 2020 14:29:34 -0500 (EST) Received: from smtpin16.hostedemail.com (10.5.19.251.rfc1918.com [10.5.19.251]) by forelay02.hostedemail.com (Postfix) with ESMTP id BEE4B3642 for ; Sun, 20 Dec 2020 19:29:34 +0000 (UTC) X-FDA: 77614649868.16.fact26_3516e6527451 Received: from filter.hostedemail.com (10.5.16.251.rfc1918.com [10.5.16.251]) by smtpin16.hostedemail.com (Postfix) with ESMTP id 9D4A3100E692B for ; Sun, 20 Dec 2020 19:29:34 +0000 (UTC) X-HE-Tag: fact26_3516e6527451 X-Filterd-Recvd-Size: 2866 Received: from casper.infradead.org (casper.infradead.org [90.155.50.34]) by imf09.hostedemail.com (Postfix) with ESMTP for ; Sun, 20 Dec 2020 19:29:32 +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=G12mo3on+EgR0F+Ws+rlPcnka9Hnel81jsJCl4EDG3w=; b=fVAAYeRmNX8lFwDmUFpgZaxgLS uG2+jGg4yjI88/ta4yxPcSaGQ65eVm896JpGLrix0cg9sGKV7r1pHi/PUq69Z6V5x+zOi/JntjUHb AhnXOpEjgOXEflstUdzpWc9cfdDKOrtNtIqzwJjeIgw2pC+WGq2nOtYs/FLe2b5MeF/fP6Nb26wvd IrwFm5zY5pYP7szYDx3Uppgq4ebPNfEf6PFhIRfo6lHAkfnMeadlfr1DB6VzecVv4BCzTY5zdvSaZ Krvg+fdISl2KsuNq2/4sRNsmNjPYxkVjznbVSAYWS4YtIY/ctAk8xt03pidf9wBpuwuHozWVr0Qrl X1jobCrg==; Received: from willy by casper.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1kr4OX-00079b-U7; Sun, 20 Dec 2020 19:29:29 +0000 Date: Sun, 20 Dec 2020 19:29:29 +0000 From: Matthew Wilcox To: "Jason A. Donenfeld" Cc: Linux-MM Subject: Re: "tell us why you want to disable CONFIG_COMPACTION" --> spikes from VMs? Message-ID: <20201220192929.GW15600@casper.infradead.org> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Sat, Dec 19, 2020 at 07:48:58PM +0100, Jason A. Donenfeld wrote: > Hi, > > In trying to debug an issue, I came across this text in the config > COMPACTION menu item: > > > Compaction is the only memory management component to form > > high order (larger physically contiguous) memory blocks > > reliably. The page allocator relies on compaction heavily and > > the lack of the feature can lead to unexpected OOM killer > > invocations for high order memory requests. You shouldn't > > disable this option unless there really is a strong reason for > > it and then we would be really interested to hear about that at > > linux-mm@kvack.org. > > So, here I am as requested. > > My system has 64 gigs of ram. Often times when starting up VMs, with > either QEMU/KVM or with VMware, the VM will be extremely sluggish and > laggy for a little while, usually around 5 minutes. During that phase, > I see kcompact0 using 100% CPU. But other times this doesn't happen at > all. I figured I'd try removing CONFIG_COMPACTION and seeing what > happens, but then I saw your admonishment, so here I am. My initial question is "What is kcompactd doing?" There are a number of tracepoints in kcompactd, so you should be able to enable them all and find out.