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=-0.6 required=3.0 tests=DKIM_SIGNED,DKIM_VALID, DKIM_VALID_AU,FREEMAIL_FORGED_FROMDOMAIN,FREEMAIL_FROM, 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 8504DC33CAB for ; Mon, 13 Jan 2020 01:32:21 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5AB2921556 for ; Mon, 13 Jan 2020 01:32:21 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="bavqG7Bb" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732415AbgAMBcS (ORCPT ); Sun, 12 Jan 2020 20:32:18 -0500 Received: from mail-oi1-f195.google.com ([209.85.167.195]:43839 "EHLO mail-oi1-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1727222AbgAMBcS (ORCPT ); Sun, 12 Jan 2020 20:32:18 -0500 Received: by mail-oi1-f195.google.com with SMTP id p125so6821638oif.10; Sun, 12 Jan 2020 17:32:18 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=MMBytJUvPgAu+zMfgqDgk/AfX9Yfe5/T6E8UlbQLhRg=; b=bavqG7BbIXENsNo9UOozQb1Br1Q21nNEU7hk7Iyb1e5fPuCq659TKTxQcBnyLyK8iN VnFlSKggY1A4gcBuyqEQf1AsRpw9Z6DefQnra9k9TSquQQLmdnFuz3SYnA5sqq7kiJC9 rIfAZQXUmG3LNRog65z5m1zZyAjNyuD3ccecWyRVh7XWsCyeU0S0gH6c5CFkrn3citxc VjfBCYx2f1Bb9sSqaUQwSnmCEg+9dhle+WZAiHosYYH/E7g7wvT8BvwDURbEAEcusB4u E/SXBAGwI+00vIHETPisSrbgOqpxvmIUiUo2pL1R4A8lykgG64v0wXEPiR0yCdrBQTmZ JXnQ== 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=MMBytJUvPgAu+zMfgqDgk/AfX9Yfe5/T6E8UlbQLhRg=; b=T3vYBf4dqyhd7l8zEfKqY9RFEYjuWfQFSDKu3XjqPSQBDa5bg6c8Ziq/+WFqEdgZLg bmlYJeS90Vc/kPFFCQeGRhfxU705NuOg0H/6jWjzPxLNeiLl7Kjif3T2mOZcdvLlm+pi kLttqLQ6u2TLzApuHKydJJEdkUWXg9BrJe7qp8ocjGXRX930dTfqdHe2fVbOfwyo2oQg rA2N7JCYv8SrQR7sWVGQZ/8hx9WeNfbJVLR4CE2UvqmG0PQ4BiOHLXZiaw6FXHjpjeoW pUSJqXuJBIQq9Ik/l2h9U2qj45fSrCNegyHCGL6/eKZdRsgMt4cRUFg5SLwGOEaD20R+ z2Xg== X-Gm-Message-State: APjAAAW2KmImYKQFI7Pn/y5WjZvD6gUUKMKVA49hfWirt50q32iaJSYd X/cp+F+NOn/iLNCpEgMf//JKvsuxS9Bd7hqCI6k= X-Google-Smtp-Source: APXvYqwCPuqbYAG95luf4ZYYWjcaCVybJvsz8csO3YSbyw59b9EkPjN9oGmKDDBpKx1Q1quoOXGu4QhIj6WTgo+7q7g= X-Received: by 2002:aca:8d5:: with SMTP id 204mr10286701oii.141.1578879137785; Sun, 12 Jan 2020 17:32:17 -0800 (PST) MIME-Version: 1.0 References: <87a76v8knv.fsf@nanos.tec.linutronix.de> In-Reply-To: <87a76v8knv.fsf@nanos.tec.linutronix.de> From: Wanpeng Li Date: Mon, 13 Jan 2020 09:32:06 +0800 Message-ID: Subject: Re: [PATCH v2] sched/nohz: Optimize get_nohz_timer_target() To: Thomas Gleixner Cc: LKML , Ingo Molnar , Peter Zijlstra , Ingo Molnar , kvm , Frederic Weisbecker Content-Type: text/plain; charset="UTF-8" Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org On Fri, 10 Jan 2020 at 22:12, Thomas Gleixner wrote: > > Wanpeng, > > Wanpeng Li writes: > > > Hi Thomas, > > On Wed, 23 Oct 2019 at 16:29, Thomas Gleixner wrote: > >> > >> On Wed, 23 Oct 2019, Wanpeng Li wrote: > >> > I didn't see your refactor to get_nohz_timer_target() which you > >> > mentioned in IRC after four months, I can observe cyclictest drop from > >> > 4~5us to 8us in kvm guest(we offload the lapic timer emulation to > >> > housekeeping cpu to avoid timer fire external interrupt on the pCPU > >> > which vCPU resident incur a vCPU vmexit) w/o this patch in the case of > >> > there is no busy housekeeping cpu. The score can be recovered after I > >> > give stress to create a busy housekeeping cpu. > >> > > >> > Could you consider applying this patch for temporary since I'm not > >> > sure when the refactor can be ready. > >> > >> Yeah. It's delayed (again).... Will pick that up. > > > > I didn't find WIP tag for this work after ~half year since v4 was > > posted https://lkml.org/lkml/2019/6/28/231 Could you apply this patch > > for temporary because the completion time of refactor is not > > deterministic. > > Could you please repost it? Just repost, thanks Thomas. Wanpeng