From: Josh Stone <jistone@redhat.com>
To: Steven Rostedt <rostedt@goodmis.org>,
linux-kernel@vger.kernel.org,
Rober Richter <robert.richter@amd.com>,
anil.s.keshavamurthy@intel.com, ananth@in.ibm.com,
davem@davemloft.net, mhiramat@redhat.com,
SystemTap <systemtap@sources.redhat.com>,
Eric Anholt <eric@anholt.net>,
Chris Wilson <chris@chris-wilson.co.uk>,
intel-gfx@lists.freedesktop.org
Subject: Re: Infrastructure for tracking driver performance events
Date: Wed, 24 Jun 2009 18:53:00 -0000 [thread overview]
Message-ID: <4A427631.4090609@redhat.com> (raw)
In-Reply-To: <20090624172912.GB5565@ben-laptop>
On 06/24/2009 10:29 AM, Ben Gamari wrote:
[...]
> I recently wrote a very simple patch to add accounting for these types
> of stalls to the i915 driver[1], exposing a list of wait-event counts to
> userspace through debugfs. While this is useful for giving a general
> overview of the drivers' performance, it does very little to expose
> individual bottlenecks in the driver or userland components. It has been
> suggested[2] that this wait-event tracking functionality would be far more
> useful if we could provide stack backtraces all the way into user space
> for each wait event.
[...]
> Another option seems to be systemtap. It has already been documented[3]
> that this option could provide both user-mode and kernel-mode
> backtraces. The driver could provide a kernel marker at every potential
> wait point (or a single marker in a function called at each wait point,
> for that matter) which would be picked up by systemtap and processed in
> usermode, calling ptrace to acquire a usermode backtrace. This approach
> seems slightly cleaner as it doesn't require the tracing on the entire
> machine to catch what should be reasonably rare events (hopefully).
>
> Unfortunately, the systemtap approach described in [3] requires that
> each process have an associated "driver" process to get a usermode
> backtrace. It would be nice to avoid this requirement as there are
> generally far more gpu clients than just the X server (i.e. direct
> rendering clients) and tracking them all could get tricky.
[...]
> [3] http://sourceware.org/ml/systemtap/2006-q4/msg00198.html
I have to say, I'm a bit surprised to see my hacky suggestion
resurrected from the archives. :) I would guess that that approach
would add way too much overhead to be of use in diagnosing stalls though.
However, I think we can do a lot better with systemtap these days.
We're growing the ability to do userspace backtraces[1] directly within
your systemtap script, which should be much less intrusive.
Please take a look at ubacktrace() and family in recent systemtap and
let us know how you think it could improve.
Thanks,
Josh
[1] http://sourceware.org/ml/systemtap/2009-q2/msg00364.html
next prev parent reply other threads:[~2009-06-24 18:53 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2009-06-24 17:29 Ben Gamari
2009-06-24 18:53 ` Josh Stone [this message]
2009-06-25 12:56 ` Steven Rostedt
2009-06-25 13:25 ` Mark Wielaard
-- strict thread matches above, loose matches on Subject: below --
2009-06-24 17:09 Ben Gamari
2009-06-24 19:58 ` Frank Ch. Eigler
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=4A427631.4090609@redhat.com \
--to=jistone@redhat.com \
--cc=ananth@in.ibm.com \
--cc=anil.s.keshavamurthy@intel.com \
--cc=chris@chris-wilson.co.uk \
--cc=davem@davemloft.net \
--cc=eric@anholt.net \
--cc=intel-gfx@lists.freedesktop.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mhiramat@redhat.com \
--cc=robert.richter@amd.com \
--cc=rostedt@goodmis.org \
--cc=systemtap@sources.redhat.com \
/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 a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).