From: Dennis Gnad <dennis.gnad@kit.edu>
To: Vince Weaver <vincent.weaver@maine.edu>
Cc: David Ahern <dsahern@gmail.com>, linux-perf-users@vger.kernel.org
Subject: Re: Understanding timestamps in perf.data
Date: Thu, 3 Sep 2015 16:46:54 +0200 [thread overview]
Message-ID: <55E85D5E.90400@kit.edu> (raw)
In-Reply-To: <alpine.DEB.2.20.1509030849190.3450@vincent-weaver-1.umelst.maine.edu>
On 03.09.2015 14:52, Vince Weaver wrote
>
> The kernel itself has trouble going to 100Hz without causing a lot of
> overhead and at 1kHz the NMI overhead gets high enough that the kernel
> throttles things down. I haven't investigated why that is, it might be a
> problem with how my tool is coded. For now I just gave up and am making
> masurements at 10Hz.
OK thanks for this information. I can probably now exclude the current
perf-interface of the kernel.
Maybe this is also interesting for you then:
In the meantime I got some information for the x86 architecture. There,
the performance counters can be read directly in userspace by the
interface over MSR's similar to readmsr/msrtool, where a reliable
interval of <10ms can be achieved. [1]
For ARM, there seems to exist some specialized driver "gator" which I
didn't take a closer look.
Anyhow, I am currently looking at a Power7 system, and don't know of any
other interfaces there than perf/oprofile. I will continue to try to
find some more information about that.
Best regards,
Dennis
[1] *F. Oboril*, J. Ewert, and M. B. Tahoori, "High-Resolution Online
Power Monitoring for Modern Microprocessors," in Proceedings of Design,
Automation & Test in Europe (*DATE*), 2015, France. Online available:
*http://cdnc.itec.kit.edu/downloads/Papers/Oboril15DATE.pdf
*
next prev parent reply other threads:[~2015-09-03 14:47 UTC|newest]
Thread overview: 13+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-09-02 9:28 Understanding timestamps in perf.data Dennis Gnad
2015-09-02 13:43 ` David Ahern
2015-09-02 15:18 ` Dennis Gnad
2015-09-02 16:44 ` David Ahern
2015-09-02 17:00 ` Vince Weaver
2015-09-02 17:00 ` David Ahern
2015-09-03 7:19 ` Dennis Gnad
2015-09-03 12:52 ` Vince Weaver
2015-09-03 14:46 ` Dennis Gnad [this message]
2015-09-03 15:17 ` Vince Weaver
2015-09-02 19:23 ` Andi Kleen
2015-09-02 19:25 ` David Ahern
2015-09-03 9:50 ` Dennis Gnad
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=55E85D5E.90400@kit.edu \
--to=dennis.gnad@kit.edu \
--cc=dsahern@gmail.com \
--cc=linux-perf-users@vger.kernel.org \
--cc=vincent.weaver@maine.edu \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.