From nobody Thu May 2 21:13:41 2024 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 1495230986163599.2478348380124; Fri, 19 May 2017 14:56:26 -0700 (PDT) Received: from localhost ([::1]:60366 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dBpsm-0001fO-5z for importer@patchew.org; Fri, 19 May 2017 17:56:24 -0400 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56831) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dBpru-0001NU-HA for qemu-devel@nongnu.org; Fri, 19 May 2017 17:55:31 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1dBprp-00022L-Qr for qemu-devel@nongnu.org; Fri, 19 May 2017 17:55:30 -0400 Received: from [62.254.189.133] (port=54277 helo=centos.localdomain) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1dBprp-0001qw-5U for qemu-devel@nongnu.org; Fri, 19 May 2017 17:55:25 -0400 Received: by centos.localdomain (Postfix, from userid 500) id BB7FB9FBD4; Fri, 19 May 2017 22:29:58 +0100 (BST) From: Felipe Franciosi To: Paolo Bonzini , "Jason J. Herne" , Malcolm Crossley Date: Fri, 19 May 2017 22:29:50 +0100 Message-Id: <1495229390-18909-1-git-send-email-felipe@nutanix.com> X-Mailer: git-send-email 1.9.5 X-detected-operating-system: by eggs.gnu.org: Mac OS X [generic] [fuzzy] X-Received-From: 62.254.189.133 Subject: [Qemu-devel] [PATCH] cpus: reset throttle_thread_scheduled after sleep 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: "qemu-devel@nongnu.org" , Felipe Franciosi 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" Currently, the throttle_thread_scheduled flag is reset back to 0 before sleeping (as part of the throttling logic). Given that throttle_timer (well, any timer) may tick with a slight delay, it so happens that under heavy throttling (ie. close or on CPU_THROTTLE_PCT_MAX) the tick may schedule a further cpu_throttle_thread() work item after the flag reset, but before the previous sleep completed. This results on the vCPU thread sleeping continuously for potentially several seconds in a row. The chances of that happening can be drastically minimised by resetting the flag after the sleep. Signed-off-by: Felipe Franciosi Signed-off-by: Malcolm Crossley Acked-by: Jason J. Herne Reviewed-by: Juan Quintela --- cpus.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/cpus.c b/cpus.c index 516e5cb..f42eebd 100644 --- a/cpus.c +++ b/cpus.c @@ -677,9 +677,9 @@ static void cpu_throttle_thread(CPUState *cpu, run_on_c= pu_data opaque) sleeptime_ns =3D (long)(throttle_ratio * CPU_THROTTLE_TIMESLICE_NS); =20 qemu_mutex_unlock_iothread(); - atomic_set(&cpu->throttle_thread_scheduled, 0); g_usleep(sleeptime_ns / 1000); /* Convert ns to us for usleep call */ qemu_mutex_lock_iothread(); + atomic_set(&cpu->throttle_thread_scheduled, 0); } =20 static void cpu_throttle_timer_tick(void *opaque) --=20 1.9.5