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=-5.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SIGNED_OFF_BY,SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED, USER_AGENT_SANE_1 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 4E69BC43331 for ; Thu, 5 Sep 2019 19:57:43 +0000 (UTC) Received: from lists.gnu.org (lists.gnu.org [209.51.188.17]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 9B50920692 for ; Thu, 5 Sep 2019 19:57:43 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 9B50920692 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com Authentication-Results: mail.kernel.org; spf=pass smtp.mailfrom=qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Received: from localhost ([::1]:49328 helo=lists1p.gnu.org) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i5xt0-0002xt-82 for qemu-devel@archiver.kernel.org; Thu, 05 Sep 2019 15:57:42 -0400 Received: from eggs.gnu.org ([2001:470:142:3::10]:51956) by lists.gnu.org with esmtp (Exim 4.90_1) (envelope-from ) id 1i5xsL-0002ZG-V3 for qemu-devel@nongnu.org; Thu, 05 Sep 2019 15:57:03 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1i5xsK-0005UO-3W for qemu-devel@nongnu.org; Thu, 05 Sep 2019 15:57:01 -0400 Received: from mx1.redhat.com ([209.132.183.28]:38210) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1i5xsJ-0005TP-Rb for qemu-devel@nongnu.org; Thu, 05 Sep 2019 15:57:00 -0400 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.phx2.redhat.com [10.5.11.23]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 5E965877A63; Thu, 5 Sep 2019 19:56:58 +0000 (UTC) Received: from [10.3.116.234] (ovpn-116-234.phx2.redhat.com [10.3.116.234]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 350BD194B9; Thu, 5 Sep 2019 19:56:57 +0000 (UTC) To: Yury Kotov , Paolo Bonzini , Richard Henderson , Juan Quintela , "Dr. David Alan Gilbert" , Thomas Huth , Laurent Vivier , Stefan Weil References: <20190826103726.25538-1-yury-kotov@yandex-team.ru> <20190826103726.25538-3-yury-kotov@yandex-team.ru> From: Eric Blake Openpgp: preference=signencrypt Autocrypt: addr=eblake@redhat.com; keydata= xsBNBEvHyWwBCACw7DwsQIh0kAbUXyqhfiKAKOTVu6OiMGffw2w90Ggrp4bdVKmCaEXlrVLU xphBM8mb+wsFkU+pq9YR621WXo9REYVIl0FxKeQo9dyQBZ/XvmUMka4NOmHtFg74nvkpJFCD TUNzmqfcjdKhfFV0d7P/ixKQeZr2WP1xMcjmAQY5YvQ2lUoHP43m8TtpB1LkjyYBCodd+LkV GmCx2Bop1LSblbvbrOm2bKpZdBPjncRNob73eTpIXEutvEaHH72LzpzksfcKM+M18cyRH+nP sAd98xIbVjm3Jm4k4d5oQyE2HwOur+trk2EcxTgdp17QapuWPwMfhaNq3runaX7x34zhABEB AAHNHkVyaWMgQmxha2UgPGVibGFrZUByZWRoYXQuY29tPsLAegQTAQgAJAIbAwULCQgHAwUV CgkICwUWAgMBAAIeAQIXgAUCS8fL9QIZAQAKCRCnoWtKJSdDahBHCACbl/5FGkUqJ89GAjeX RjpAeJtdKhujir0iS4CMSIng7fCiGZ0fNJCpL5RpViSo03Q7l37ss+No+dJI8KtAp6ID+PMz wTJe5Egtv/KGUKSDvOLYJ9WIIbftEObekP+GBpWP2+KbpADsc7EsNd70sYxExD3liwVJYqLc Rw7so1PEIFp+Ni9A1DrBR5NaJBnno2PHzHPTS9nmZVYm/4I32qkLXOcdX0XElO8VPDoVobG6 gELf4v/vIImdmxLh/w5WctUpBhWWIfQDvSOW2VZDOihm7pzhQodr3QP/GDLfpK6wI7exeu3P pfPtqwa06s1pae3ad13mZGzkBdNKs1HEm8x6zsBNBEvHyWwBCADGkMFzFjmmyqAEn5D+Mt4P zPdO8NatsDw8Qit3Rmzu+kUygxyYbz52ZO40WUu7EgQ5kDTOeRPnTOd7awWDQcl1gGBXgrkR pAlQ0l0ReO57Q0eglFydLMi5bkwYhfY+TwDPMh3aOP5qBXkm4qIYSsxb8A+i00P72AqFb9Q7 3weG/flxSPApLYQE5qWGSXjOkXJv42NGS6o6gd4RmD6Ap5e8ACo1lSMPfTpGzXlt4aRkBfvb NCfNsQikLZzFYDLbQgKBA33BDeV6vNJ9Cj0SgEGOkYyed4I6AbU0kIy1hHAm1r6+sAnEdIKj cHi3xWH/UPrZW5flM8Kqo14OTDkI9EtlABEBAAHCwF8EGAEIAAkFAkvHyWwCGwwACgkQp6Fr SiUnQ2q03wgAmRFGDeXzc58NX0NrDijUu0zx3Lns/qZ9VrkSWbNZBFjpWKaeL1fdVeE4TDGm I5mRRIsStjQzc2R9b+2VBUhlAqY1nAiBDv0Qnt+9cLiuEICeUwlyl42YdwpmY0ELcy5+u6wz mK/jxrYOpzXKDwLq5k4X+hmGuSNWWAN3gHiJqmJZPkhFPUIozZUCeEc76pS/IUN72NfprZmF Dp6/QDjDFtfS39bHSWXKVZUbqaMPqlj/z6Ugk027/3GUjHHr8WkeL1ezWepYDY7WSoXwfoAL 2UXYsMAr/uUncSKlfjvArhsej0S4zbqim2ZY6S8aRWw94J3bSvJR+Nwbs34GPTD4Pg== Organization: Red Hat, Inc. Message-ID: <57c35118-a8c4-83cd-6f14-4e428a75238d@redhat.com> Date: Thu, 5 Sep 2019 14:56:56 -0500 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190826103726.25538-3-yury-kotov@yandex-team.ru> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 7bit X-Scanned-By: MIMEDefang 2.84 on 10.5.11.23 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.6.2 (mx1.redhat.com [10.5.110.69]); Thu, 05 Sep 2019 19:56:58 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] X-Received-From: 209.132.183.28 Subject: Re: [Qemu-devel] [PATCH v5 2/3] cpus: Fix throttling during vm_stop X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.23 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: "open list:Overall" , "yc-core@yandex-team.ru" Errors-To: qemu-devel-bounces+qemu-devel=archiver.kernel.org@nongnu.org Sender: "Qemu-devel" On 8/26/19 5:37 AM, Yury Kotov wrote: > Throttling thread sleeps in VCPU thread. For high throttle percentage > this sleep is more than 10ms. E.g. for 60% - 15ms, for 99% - 990ms. > vm_stop() kicks all VCPUs and waits for them. It's called at the end of > migration and because of the long sleep the migration downtime might be > more than 100ms even for downtime-limit 1ms. > Use qemu_cond_timedwait for high percentage to wake up during vm_stop. > > Signed-off-by: Yury Kotov > --- > cpus.c | 25 +++++++++++++++++-------- > 1 file changed, 17 insertions(+), 8 deletions(-) > > @@ -790,11 +792,20 @@ static void cpu_throttle_thread(CPUState *cpu, run_on_cpu_data opaque) > > pct = (double)cpu_throttle_get_percentage()/100; > throttle_ratio = pct / (1 - pct); > - sleeptime_ns = (long)(throttle_ratio * CPU_THROTTLE_TIMESLICE_NS); > - > - qemu_mutex_unlock_iothread(); > - g_usleep(sleeptime_ns / 1000); /* Convert ns to us for usleep call */ > - qemu_mutex_lock_iothread(); > + /* Add 1ns to fix double's rounding error (like 0.9999999...) */ > + sleeptime_ns = (int64_t)(throttle_ratio * CPU_THROTTLE_TIMESLICE_NS + 1); The cast to int64_t is not strictly necessary here, but doesn't hurt (since it shows you DO know you are going from double to 64-bit int). > + endtime_ns = qemu_clock_get_ns(QEMU_CLOCK_REALTIME) + sleeptime_ns; > + while (sleeptime_ns > 0 && !cpu->stop) { > + if (sleeptime_ns > SCALE_MS) { > + qemu_cond_timedwait(cpu->halt_cond, &qemu_global_mutex, > + sleeptime_ns / SCALE_MS); > + } else { > + qemu_mutex_unlock_iothread(); > + g_usleep(sleeptime_ns / SCALE_US); > + qemu_mutex_lock_iothread(); > + } > + sleeptime_ns = endtime_ns - qemu_clock_get_ns(QEMU_CLOCK_REALTIME); > + } Looks reasonable. (I wonder if an alternative approach, of doing a poll() or similar instead of g_usleep, and using a pipe-to-self where we write to the pipe in the same scenarios where cpu->halt_cond would be broadcast, in order to wake up the sleeping poll in a responsive manner, would be any easier or more efficient - but don't rewrite the patch just because of my question) Reviewed-by: Eric Blake -- Eric Blake, Principal Software Engineer Red Hat, Inc. +1-919-301-3226 Virtualization: qemu.org | libvirt.org