From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:56688) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZLDuw-000148-M4 for qemu-devel@nongnu.org; Fri, 31 Jul 2015 13:16:23 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1ZLDur-0007hF-2A for qemu-devel@nongnu.org; Fri, 31 Jul 2015 13:16:22 -0400 Received: from mail-wi0-x22a.google.com ([2a00:1450:400c:c05::22a]:37781) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1ZLDuq-0007gx-Qa for qemu-devel@nongnu.org; Fri, 31 Jul 2015 13:16:16 -0400 Received: by wibud3 with SMTP id ud3so40241279wib.0 for ; Fri, 31 Jul 2015 10:16:16 -0700 (PDT) Sender: Paolo Bonzini References: <1435855010-30882-1-git-send-email-jjherne@linux.vnet.ibm.com> <1435855010-30882-2-git-send-email-jjherne@linux.vnet.ibm.com> <55956A2E.4020806@redhat.com> <55A3CEAF.6030504@linux.vnet.ibm.com> <55A3D5D8.7070902@redhat.com> <55A654D6.5000906@linux.vnet.ibm.com> <55A657ED.3070407@redhat.com> <55A7BDF4.4020509@linux.vnet.ibm.com> <55B0BAE6.3040504@redhat.com> <55BBAC8F.6030604@linux.vnet.ibm.com> From: Paolo Bonzini Message-ID: <55BBAD5D.4090807@redhat.com> Date: Fri, 31 Jul 2015 19:16:13 +0200 MIME-Version: 1.0 In-Reply-To: <55BBAC8F.6030604@linux.vnet.ibm.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v4 1/5] cpu: Provide vcpu throttling interface List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: jjherne@linux.vnet.ibm.com, afaerber@suse.de, amit.shah@redhat.com, dgilbert@redhat.com, borntraeger@de.ibm.com, quintela@redhat.com, qemu-devel@nongnu.org On 31/07/2015 19:12, Jason J. Herne wrote: >> >> > > Throttle ratio is relative to CPU_THROTTLE_TIMESLICE. Take a look at how > throttle_ratio is used in the calculation: > > long sleeptime_ms = (long)(throttle_ratio * CPU_THROTTLE_TIMESLICE); > > A value of 1 means we sleep the same amount of time that we execute. But that doesn't work if your timer runs every CPU_THROTTLE_TIMESLICE milliseconds, and thus schedules async work every CPU_THROTTLE_TIMESLICE milliseconds. The timer would have to be scheduled every (throttle_ratio + 1) * CPU_THROTTLE_TIMESLICE milliseconds, i.e. CPU_THROTTLE_TIMESLICE / (1-pct) milliseconds. Paolo