Messages in this thread | | | Subject | Re: [PATCH] x86/xen: Add "xen_timer_slop" command line option | From | Dario Faggioli <> | Date | Sat, 23 Mar 2019 03:58:16 +0100 |
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On Fri, 2019-03-22 at 18:10 -0400, Boris Ostrovsky wrote: > On 3/22/19 2:29 PM, thibodux@gmail.com wrote: > > From: Ryan Thibodeaux <ryan.thibodeaux@starlab.io> > > > > The original timer slop value has not changed since the > > introduction > > of the Xen-aware Linux kernel code. This commit provides users an > > opportunity to tune timer performance given the refinements to > > hardware and the Xen event channel processing. It also mirrors > > a feature in the Xen hypervisor - the "timer_slop" Xen command line > > option. > > Is there any data that shows effects of using this new parameter? > Yes, I've done some research and experiments on this. I did it together with a friend, which I'm Cc-ing, as I'm not sure we're ready/capable to share the results, yet (Luca?).
What I think I can anticipate is that having such a high value for timer slop in the kernel, for the Xen clockevent device is (together with the also quite high default value of timer_slop in Xen itself) responsible for really high vcpu wakeup latencies.
Lowering those two values, reduces such latencies dramatically.
Regards, Dario -- <<This happens because I choose it to happen!>> (Raistlin Majere) ----------------------------------------------------------------- Dario Faggioli, Ph.D, http://about.me/dario.faggioli Software Engineer @ SUSE https://www.suse.com/ [unhandled content-type:application/pgp-signature] | |