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=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, MAILING_LIST_MULTI,SPF_PASS,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 14E2EC04EB9 for ; Mon, 3 Dec 2018 16:16:40 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id CA72C20881 for ; Mon, 3 Dec 2018 16:16:39 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="Q36ZJtc9" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org CA72C20881 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.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 S1726779AbeLCQQp (ORCPT ); Mon, 3 Dec 2018 11:16:45 -0500 Received: from mail-yw1-f67.google.com ([209.85.161.67]:35460 "EHLO mail-yw1-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726608AbeLCQQp (ORCPT ); Mon, 3 Dec 2018 11:16:45 -0500 Received: by mail-yw1-f67.google.com with SMTP id h32so5611242ywk.2; Mon, 03 Dec 2018 08:16:37 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=sender:date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to:user-agent; bh=Zyej+P76eFYO88X75IO3hiKMFBZsjaA/oPu+bdOeXog=; b=Q36ZJtc9jhXRNvwwyFmz6XweAG5R2x3fD/KaHvyNiLRebwVBuouKSjNnxlmjuo0e87 hYroaWLAjaEShMoVApHVKCmbVUjoBeJMvW5cOFr8D9Ej02Nb1j2hpZmlrafP3EOo9j/d +0dAdq+CUrd0JklJv4RY2NmXbAKGiqBFlLv4qAcmvknOtGPtAZsskAEy2ln3GzHyQFNK SYyslHdtdcfzX5HqGbPSZp4JFaUk5RcUAXdE1i33JhnEITRTFoJF64rzwIndP+nw9dLU f+w4w6sXrZI9UbKlnFgzfk4L+TaRX+qyOede0iiOLQbvUZnEadMOu6S/HNXCNBOrB3ZI NXWw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:sender:date:from:to:cc:subject:message-id :references:mime-version:content-disposition:in-reply-to:user-agent; bh=Zyej+P76eFYO88X75IO3hiKMFBZsjaA/oPu+bdOeXog=; b=hgBYoMo/ac7zuIwa/0wdvBgiBt83n8DYkUZuw1UkXdW6PSHRonxL6+Gk4RuNuefXXZ PTdwn86uyCkZ+z6P9waDmbUAFCC9i2VTLxgV9+Hq9u7YARbG9Lopf7oQriZYL7U3skv4 WRlXgyrV93l0Eazj1liVwV3p8kNmYn8hwf2Fc0M4XAc6oioW0chBl1D5Ems54RNjq8UA RxSI71O9j03MopgwcEcrucjjX0nnGeAgnn9fnRBzyE5RcS/Dq3bLXMcgEwBYNbWrCYkW soHzl+Yk2/eCXdvehtPgHWyBP3orxOrTqpXbGqP9HTgpN6+FDGNqamKnv4IM/tnR/v0f Hsxw== X-Gm-Message-State: AA+aEWa+qxJMVPpBsuZX5mI95DsDKyOVkUGulJWKX1y6Yu97ZgvKwF/m zFt2hH0Crtwyh36JMZCBgCs= X-Google-Smtp-Source: AFSGD/WDhW6Tkie0JLjKRTkPTLbiDCCnzJoZTzmHxZo4+koB/r/mpbqawg6suWa97v1xtwWYNK8xLg== X-Received: by 2002:a81:3194:: with SMTP id x142mr15441540ywx.92.1543853796911; Mon, 03 Dec 2018 08:16:36 -0800 (PST) Received: from localhost ([2620:10d:c091:200::5:20d7]) by smtp.gmail.com with ESMTPSA id w1sm4365697ywd.49.2018.12.03.08.16.35 (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 03 Dec 2018 08:16:35 -0800 (PST) Date: Mon, 3 Dec 2018 08:16:33 -0800 From: Tejun Heo To: Daniel Jordan Cc: linux-mm@kvack.org, kvm@vger.kernel.org, linux-kernel@vger.kernel.org, aarcange@redhat.com, aaron.lu@intel.com, akpm@linux-foundation.org, alex.williamson@redhat.com, bsd@redhat.com, darrick.wong@oracle.com, dave.hansen@linux.intel.com, jgg@mellanox.com, jwadams@google.com, jiangshanlai@gmail.com, mhocko@kernel.org, mike.kravetz@oracle.com, Pavel.Tatashin@microsoft.com, prasad.singamsetty@oracle.com, rdunlap@infradead.org, steven.sistare@oracle.com, tim.c.chen@intel.com, vbabka@suse.cz, peterz@infradead.org, dhaval.giani@oracle.com Subject: Re: [RFC PATCH v4 00/13] ktask: multithread CPU-intensive kernel work Message-ID: <20181203161633.GK2509588@devbig004.ftw2.facebook.com> References: <20181105165558.11698-1-daniel.m.jordan@oracle.com> <20181130191819.GJ2509588@devbig004.ftw2.facebook.com> <20181201001307.wmb6o4fuysnl7vcz@ca-dmjordan1.us.oracle.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181201001307.wmb6o4fuysnl7vcz@ca-dmjordan1.us.oracle.com> User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Hello, On Fri, Nov 30, 2018 at 04:13:07PM -0800, Daniel Jordan wrote: > On Fri, Nov 30, 2018 at 11:18:19AM -0800, Tejun Heo wrote: > > Hello, > > > > On Mon, Nov 05, 2018 at 11:55:45AM -0500, Daniel Jordan wrote: > > > Michal, you mentioned that ktask should be sensitive to CPU utilization[1]. > > > ktask threads now run at the lowest priority on the system to avoid disturbing > > > busy CPUs (more details in patches 4 and 5). Does this address your concern? > > > The plan to address your other comments is explained below. > > > > Have you tested what kind of impact this has on bandwidth of a system > > in addition to latency? The thing is while this would make a better > > use of a system which has idle capacity, it does so by doing more > > total work. It'd be really interesting to see how this affects > > bandwidth of a system too. > > I guess you mean something like comparing aggregate CPU time across threads to > the base single thread time for some job or set of jobs? Then no, I haven't > measured that, but I can for next time. Yeah, I'm primarily curious how expensive this is on an already loaded system, so sth like loading up the system with a workload which can saturate the system and comparing the bw impacts of serial and parallel page clearings at the same frequency. Thanks. -- tejun