From nobody Sun Feb 8 14:52:14 2026 Delivered-To: importer@patchew.org Received-SPF: pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) client-ip=208.118.235.17; envelope-from=qemu-devel-bounces+importer=patchew.org@nongnu.org; helo=lists.gnu.org; Authentication-Results: mx.zoho.com; spf=pass (zoho.com: domain of gnu.org designates 208.118.235.17 as permitted sender) smtp.mailfrom=qemu-devel-bounces+importer=patchew.org@nongnu.org; Return-Path: Received: from lists.gnu.org (lists.gnu.org [208.118.235.17]) by mx.zohomail.com with SMTPS id 1490599599127110.74007885164144; Mon, 27 Mar 2017 00:26:39 -0700 (PDT) Received: from localhost ([::1]:44794 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1csP30-0000yx-0D for importer@patchew.org; Mon, 27 Mar 2017 03:26:38 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:50756) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1csOzT-0006fr-3P for qemu-devel@nongnu.org; Mon, 27 Mar 2017 03:23:00 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1csOzS-00036W-5f for qemu-devel@nongnu.org; Mon, 27 Mar 2017 03:22:59 -0400 Received: from mx1.redhat.com ([209.132.183.28]:59886) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1csOzR-00036D-Vd for qemu-devel@nongnu.org; Mon, 27 Mar 2017 03:22:58 -0400 Received: from smtp.corp.redhat.com (int-mx06.intmail.prod.int.phx2.redhat.com [10.5.11.16]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 13276C065107; Mon, 27 Mar 2017 07:22:57 +0000 (UTC) Received: from pxdev.xzpeter.org (vpn1-7-78.pek2.redhat.com [10.72.7.78]) by smtp.corp.redhat.com (Postfix) with ESMTP id 41813BA889; Mon, 27 Mar 2017 07:22:50 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mx1.redhat.com 13276C065107 Authentication-Results: ext-mx07.extmail.prod.ext.phx2.redhat.com; dmarc=none (p=none dis=none) header.from=redhat.com Authentication-Results: ext-mx07.extmail.prod.ext.phx2.redhat.com; spf=pass smtp.mailfrom=peterx@redhat.com DKIM-Filter: OpenDKIM Filter v2.11.0 mx1.redhat.com 13276C065107 From: Peter Xu To: qemu-devel@nongnu.org Date: Mon, 27 Mar 2017 15:21:28 +0800 Message-Id: <1490599288-11751-6-git-send-email-peterx@redhat.com> In-Reply-To: <1490599288-11751-1-git-send-email-peterx@redhat.com> References: <1490599288-11751-1-git-send-email-peterx@redhat.com> X-Scanned-By: MIMEDefang 2.79 on 10.5.11.16 X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.5.16 (mx1.redhat.com [10.5.110.31]); Mon, 27 Mar 2017 07:22:57 +0000 (UTC) X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.2.x-3.x [generic] [fuzzy] X-Received-From: 209.132.183.28 Subject: [Qemu-devel] [PATCH 5/5] cpu: throttle: fix throttle time slice X-BeenThere: qemu-devel@nongnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: Juan Quintela , "\\ Dr . David Alan Gilbert \\ " , peterx@redhat.com, "Jason J . Herne" , Paolo Bonzini , Richard Henderson Errors-To: qemu-devel-bounces+importer=patchew.org@nongnu.org Sender: "Qemu-devel" X-ZohoMail: RSF_0 Z_629925259 SPT_0 Content-Transfer-Encoding: quoted-printable MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" IIUC the throttle idea is that: we split a CPU_THROTTLE_TIMESLICE_NS time slice into two parts - one for vcpu, one for throttle thread (which will suspend the thread by a sleep). However current algorithm on calculating the working piece and sleeping piece is strange. Assume a 99% throttle, what we want is to merely stop vcpu from running, but the old logic will just first let the vcpu run for a very long time (which is "CPU_THROTTLE_TIMESLICE_NS / (1-pct)" =3D 1 second) before doing anything else. Fixing it up to the simplest but imho accurate logic. CC: Paolo Bonzini CC: Richard Henderson CC: Jason J. Herne Signed-off-by: Peter Xu --- cpus.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-) diff --git a/cpus.c b/cpus.c index 167d961..7976ce4 100644 --- a/cpus.c +++ b/cpus.c @@ -633,7 +633,6 @@ static const VMStateDescription vmstate_timers =3D { static void cpu_throttle_thread(CPUState *cpu, run_on_cpu_data opaque) { double pct; - double throttle_ratio; long sleeptime_ns; =20 if (!cpu_throttle_get_percentage()) { @@ -641,8 +640,7 @@ static void cpu_throttle_thread(CPUState *cpu, run_on_c= pu_data opaque) } =20 pct =3D (double)cpu_throttle_get_percentage()/100; - throttle_ratio =3D pct / (1 - pct); - sleeptime_ns =3D (long)(throttle_ratio * CPU_THROTTLE_TIMESLICE_NS); + sleeptime_ns =3D (long)((1 - pct) * CPU_THROTTLE_TIMESLICE_NS); =20 qemu_mutex_unlock_iothread(); atomic_set(&cpu->throttle_thread_scheduled, 0); @@ -668,7 +666,7 @@ static void cpu_throttle_timer_tick(void *opaque) =20 pct =3D (double)cpu_throttle_get_percentage()/100; timer_mod(throttle_timer, qemu_clock_get_ns(QEMU_CLOCK_VIRTUAL_RT) + - CPU_THROTTLE_TIMESLICE_NS / (1-pct)); + CPU_THROTTLE_TIMESLICE_NS * pct); } =20 void cpu_throttle_set(int new_throttle_pct) --=20 2.7.4