From: David Ahern <dsahern@gmail.com>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Joseph Schuchart <joseph.schuchart@tu-dresden.de>,
Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Paul Mackerras <paulus@samba.org>, Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@ghostprotocols.net>,
thomas.ilsche@tu-dresden.de, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] Perf: Correct Assumptions about Sample Timestamps in Passes
Date: Wed, 01 Jan 2014 11:37:55 -0700 [thread overview]
Message-ID: <52C46083.9070605@gmail.com> (raw)
In-Reply-To: <20131226153033.GC15303@localhost.localdomain>
On 12/26/13, 8:30 AM, Frederic Weisbecker wrote:
> On Thu, Dec 26, 2013 at 10:24:03AM -0500, David Ahern wrote:
>> On 12/26/13, 10:14 AM, Frederic Weisbecker wrote:
>>>> I was carrying that patch while working on perf-kvm-stat-live last
>>>> Fall. It does not solve the problem for live commands, so ended up
>>>> dropping it and going with local (to the command) hacks. I still
>>>> think for live commands getting a perf_clock timestamp at the start
>>>> of a round and using that as the flush time will work best.
For perf-kvm-stat-live using perf_clock value at the start of the round
as the flush time works beautifully:
https://github.com/dsahern/linux/commit/ba8b7b63d5dbdc95aedbbafa670c2232e0cc07a2
Never once failed with "Warning: Timestamp below last timeslice flush"
error.
David
>>>
>>> Ok, but how would you fetch this perf clock timestamp, with an explicit read?
>>
>> One option is exporting perf_clock to userspace.
>>
>> Preferably a built-in option, https://lkml.org/lkml/2013/12/10/781,
>> but I can go the module route if I have to:
>> https://github.com/dsahern/linux/blob/perf-full-monty/README.ahern
>
> I see, that's one of the very verbose threads I've seen lately ;)
>
next prev parent reply other threads:[~2014-01-01 18:38 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-11-14 8:07 [PATCH] Perf: Correct Assumptions about Sample Timestamps in Passes Joseph Schuchart
2013-11-14 8:39 ` Ingo Molnar
2013-11-14 8:59 ` Joseph Schuchart
2013-11-14 10:05 ` Ingo Molnar
2013-11-14 14:26 ` David Ahern
2013-11-14 14:44 ` Peter Zijlstra
2013-11-14 15:02 ` David Ahern
2013-11-14 15:25 ` Peter Zijlstra
2013-11-21 14:55 ` Joseph Schuchart
2013-11-27 13:51 ` Ingo Molnar
2013-12-20 12:27 ` Joseph Schuchart
2013-12-20 17:09 ` David Ahern
2013-12-23 13:10 ` Frederic Weisbecker
2013-12-23 14:44 ` David Ahern
2013-12-26 15:14 ` Frederic Weisbecker
2013-12-26 15:24 ` David Ahern
2013-12-26 15:30 ` Frederic Weisbecker
2014-01-01 18:37 ` David Ahern [this message]
2014-01-03 22:07 ` Frederic Weisbecker
2014-01-03 22:45 ` David Ahern
2014-01-04 15:05 ` Frederic Weisbecker
2014-01-08 21:48 ` David Ahern
2014-01-09 15:19 ` Frederic Weisbecker
2014-01-12 15:46 ` David Ahern
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