From mboxrd@z Thu Jan 1 00:00:00 1970 From: Keir Fraser Subject: Re: VCPUOP_set_periodic_timer Date: Fri, 15 Nov 2013 13:39:31 +0000 Message-ID: References: <52861DE8.5060208@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: quoted-printable Return-path: In-Reply-To: <52861DE8.5060208@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Andrew Cooper Cc: Simon Martin , "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org On 15/11/2013 13:13, "Andrew Cooper" wrote: > = > On 15/11/13 13:10, Keir Fraser wrote: > = > = >> Re: Re[4]: [Xen-devel] VCPUOP_set_periodic_timer You=B9ll have to meas= ure to >> confirm, but if the core is dedicated to your vcpu then there is no reas= on >> there should be 50us jitter. Also there is not much point playing with >> different schedulers =8B if there are no other vcpus schedulable on the = cpu, >> the scheduler can=B9t have multiple runnable vcpus to choose between. >> = >> -- Keir >> = > = > The deadline timer code as up to 50us of slop when calculating when to w= ake > up and when timers expire. It is somewhat poor, and is certainly an area= in > need of improvement. Forgot about that. For real-time applications, timer_slop=3D0 on the Xen command line will turn it off. But there could certainly be other gotchas lurking; actual performance needs to be measured. -- Keir > ~Andrew > =