From: Boris Ostrovsky <boris.ostrovsky@oracle.com>
To: luca abeni <luca.abeni@santannapisa.it>,
Dario Faggioli <dfaggioli@suse.com>
Cc: thibodux@gmail.com, xen-devel@lists.xenproject.org,
linux-kernel@vger.kernel.org, oleksandr_andrushchenko@epam.com,
tglx@linutronix.de, jgross@suse.com, ryan.thibodeaux@starlab.io
Subject: Re: [PATCH] x86/xen: Add "xen_timer_slop" command line option
Date: Mon, 25 Mar 2019 09:43:20 -0400 [thread overview]
Message-ID: <69e40698-f7ae-11c3-e4b7-dda4f1fadcf6@oracle.com> (raw)
In-Reply-To: <20190325130530.56603806@luca64>
On 3/25/19 8:05 AM, luca abeni wrote:
> Hi all,
>
> On Sat, 23 Mar 2019 11:41:51 +0100
> luca abeni <luca.abeni@santannapisa.it> wrote:
> [...]
>>>> 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?).
>> I think we can easily share the experimental data (cyclictest output
>> and plots).
>>
>> Moreover, we can share the scripts and tools for running the
>> experiments (so, everyone can easily reproduce the numbers by simply
>> typing "make" and waiting for some time :)
>>
>>
>> I'll try to package the results and the scripts/tools this evening,
>> and I'll send them.
> Sorry for the delay. I put some quick results here:
> http://retis.santannapisa.it/luca/XenTimers/
> (there also is a link to the scripts to be used for reproducing the
> results). The latencies have been measured by running cyclictest in the
> guest (see the scripts for details).
>
> The picture shows the latencies measured with an unpatched guest kernel
> and with a guest kernel having TIMER_SLOP set to 1000 (arbitrary small
> value :).
> All the experiments have been performed booting the hypervisor with a
> small timer_slop (the hypervisor's one) value. So, they show that
> decreasing the hypervisor's timer_slop is not enough to measure low
> latencies with cyclictest.
I have a couple of questions:
* Does it make sense to make this a tunable for other clockevent devices
as well?
* This patch adjusts min value. Could max value (ever) need a similar
adjustment?
-boris
next prev parent reply other threads:[~2019-03-25 13:44 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
2019-03-23 10:41 ` luca abeni
2019-03-25 12:05 ` luca abeni
2019-03-25 13:43 ` Boris Ostrovsky [this message]
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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