From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andrew Cooper Subject: Re: VCPUOP_set_periodic_timer Date: Fri, 15 Nov 2013 13:13:12 +0000 Message-ID: <52861DE8.5060208@citrix.com> References: Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============2493604012922610266==" Return-path: In-Reply-To: List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Keir Fraser Cc: Simon Martin , "xen-devel@lists.xen.org" List-Id: xen-devel@lists.xenproject.org --===============2493604012922610266== Content-Type: multipart/alternative; boundary="------------060109040602010102080805" --------------060109040602010102080805 Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit On 15/11/13 13:10, Keir Fraser wrote: > Re: Re[4]: [Xen-devel] VCPUOP_set_periodic_timer You'll have to > measure to confirm, but if the core is dedicated to your vcpu then > there is no reason there should be 50us jitter. Also there is not much > point playing with different schedulers --- if there are no other > vcpus schedulable on the cpu, the scheduler can't have multiple > runnable vcpus to choose between. > > -- Keir The deadline timer code as up to 50us of slop when calculating when to wake up and when timers expire. It is somewhat poor, and is certainly an area in need of improvement. ~Andrew --------------060109040602010102080805 Content-Type: text/html; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit
On 15/11/13 13:10, Keir Fraser wrote:
Re: Re[4]: [Xen-devel] VCPUOP_set_periodic_timer You’ll have to measure to confirm, but if the core is dedicated to your vcpu then there is no reason there should be 50us jitter. Also there is not much point playing with different schedulers — if there are no other vcpus schedulable on the cpu, the scheduler can’t have multiple runnable vcpus to choose between.

 -- Keir

The deadline timer code as up to 50us of slop when calculating when to wake up and when timers expire.  It is somewhat poor, and is certainly an area in need of improvement.

~Andrew
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