From mboxrd@z Thu Jan 1 00:00:00 1970 From: George Dunlap Subject: Re: Re: performance of credit2 on hybrid workload Date: Wed, 1 Jun 2011 10:31:00 +0100 Message-ID: References: <1306340309.21026.8524.camel@elijah> <1306401493.21026.8526.camel@elijah> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xensource.com Errors-To: xen-devel-bounces@lists.xensource.com To: David Xu Cc: xen-devel@lists.xensource.com, George Dunlap List-Id: xen-devel@lists.xenproject.org You cannot do that with the current code; to add such a parameter would require major work to the scheduler. -George On Wed, Jun 1, 2011 at 1:55 AM, David Xu wrote: > Hi, > I want to reduce the latency of a specific VM. How should I do based on > credit scheduler? For example, I will add another parameter latency besid= es > weight and cap, and schedule the vcpu whose VM holds the least latency > firstly each time.=A0Thanks. > Regards, > Cong > > 2011/5/26 George Dunlap >> >> Please reply to the list. :-) >> >> Also, this is a question about credit1, so it should arguably be a >> different thread. >> >> =A0-George >> >> On Wed, 2011-05-25 at 19:34 +0100, David Xu wrote: >> > Thanks. The boost mechanism in credit can significantly reduce the >> > scheduling latency for pure I/O workload. Since the minimum interval >> > of credit scheduling is 10ms, the magnitude of latency for the target >> > VM should be 10ms (except the credit is not used up and vcpu remain >> > the head of runqueue ) as well. Why the real latency in my test (Ping >> > the target VM) is much shorter than 10ms? Does the vcpu of target VM >> > remain the head of runqueue if it was boosted? >> > >> > >> > David >> > >> > 2011/5/25 George Dunlap >> > >> > =A0 =A0 =A0 =A0 On Mon, 2011-05-23 at 09:15 +0100, David Xu wrote: >> > =A0 =A0 =A0 =A0 > Hi, >> > =A0 =A0 =A0 =A0 > >> > =A0 =A0 =A0 =A0 > >> > =A0 =A0 =A0 =A0 > Xen4.1 datasheet tells that credit2 scheduler is des= igned >> > =A0 =A0 =A0 =A0 for latency >> > =A0 =A0 =A0 =A0 > sensitive workloads. Does it have some improvement o= n the >> > =A0 =A0 =A0 =A0 hybrid >> > =A0 =A0 =A0 =A0 > workload including both the cpu-bound and latency-se= nsitive >> > =A0 =A0 =A0 =A0 i/o work? >> > =A0 =A0 =A0 =A0 > For example, if a VM runs a cpu-bound task burning t= he cpu >> > =A0 =A0 =A0 =A0 and a >> > =A0 =A0 =A0 =A0 > i/o-bound (latency-sensitive) task simultaneously, w= ill the >> > =A0 =A0 =A0 =A0 latency be >> > =A0 =A0 =A0 =A0 > guaranteed? And how? >> > >> > >> > =A0 =A0 =A0 =A0 At the moment, the "mixed workload" problem, where a s= ingle VM >> > =A0 =A0 =A0 =A0 does both >> > =A0 =A0 =A0 =A0 cpu-intensive and latency-sensitive* workloads, has no= t been >> > =A0 =A0 =A0 =A0 addressed >> > =A0 =A0 =A0 =A0 yet. =A0I have some ideas, but I haven't implemented t= hem yet. >> > >> > =A0 =A0 =A0 =A0 * i/o-bound is not the same as latency sensitive. =A0T= hey >> > =A0 =A0 =A0 =A0 obviously go >> > =A0 =A0 =A0 =A0 together frequently, but I would make a distinction be= tween >> > =A0 =A0 =A0 =A0 them. =A0For >> > =A0 =A0 =A0 =A0 example, an scp (copy over ssh) can easily become cpu-= bound if >> > =A0 =A0 =A0 =A0 there is >> > =A0 =A0 =A0 =A0 competition for the cpu -- but it is nonetheless laten= cy >> > =A0 =A0 =A0 =A0 sensitive. =A0(I >> > =A0 =A0 =A0 =A0 guess to put it another way, a workload which is >> > =A0 =A0 =A0 =A0 latency-sensitive may >> > =A0 =A0 =A0 =A0 become i/o-bound if its scheduling latency is too high= .) >> > >> > =A0 =A0 =A0 =A0 =A0-George >> > >> > >> > >> >> > > > _______________________________________________ > Xen-devel mailing list > Xen-devel@lists.xensource.com > http://lists.xensource.com/xen-devel > >