From: Dario Faggioli <dfaggioli@suse.com>
To: Boris Ostrovsky <boris.ostrovsky@oracle.com>,
thibodux@gmail.com, xen-devel@lists.xenproject.org,
linux-kernel@vger.kernel.org
Cc: oleksandr_andrushchenko@epam.com, tglx@linutronix.de,
jgross@suse.com, ryan.thibodeaux@starlab.io,
luca abeni <luca.abeni@santannapisa.it>
Subject: Re: [PATCH] x86/xen: Add "xen_timer_slop" command line option
Date: Sat, 23 Mar 2019 03:58:16 +0100 [thread overview]
Message-ID: <52bfeae7c256faec444b69efe58d363ad60c3fc5.camel@suse.com> (raw)
In-Reply-To: <abf65a68-9463-0f0e-1f51-6eefd3cacc88@oracle.com>
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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/
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next prev parent reply other threads:[~2019-03-23 2:58 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-22 18:29 [PATCH] x86/xen: Add "xen_timer_slop" command line option thibodux
2019-03-22 22:10 ` Boris Ostrovsky
2019-03-23 2:58 ` Dario Faggioli [this message]
2019-03-23 10:41 ` luca abeni
2019-03-25 12:05 ` luca abeni
2019-03-25 13:43 ` Boris Ostrovsky
2019-03-25 14:07 ` luca abeni
2019-03-25 14:11 ` Ryan Thibodeaux
2019-03-25 17:36 ` Ryan Thibodeaux
2019-03-25 18:31 ` Boris Ostrovsky
2019-03-26 9:13 ` Dario Faggioli
2019-03-26 11:12 ` luca abeni
2019-03-26 11:41 ` Ryan Thibodeaux
2019-03-26 23:21 ` Boris Ostrovsky
2019-03-27 10:00 ` Ryan Thibodeaux
2019-03-27 14:46 ` Boris Ostrovsky
2019-03-27 14:59 ` Ryan Thibodeaux
2019-03-27 15:19 ` Dario Faggioli
2019-03-23 12:00 ` Ryan Thibodeaux
2019-03-24 18:07 ` Boris Ostrovsky
2019-03-25 10:36 ` Dario Faggioli
2019-04-24 18:47 ` Boris Ostrovsky
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