From: Vince Weaver <vincent.weaver@maine.edu>
To: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@redhat.com>,
Arnaldo Carvalho de Melo <acme@kernel.org>
Subject: Re: perf: negative time_enabled issue
Date: Fri, 17 Mar 2017 10:37:48 -0400 (EDT) [thread overview]
Message-ID: <alpine.DEB.2.20.1703171035490.13039@macbook-air> (raw)
In-Reply-To: <alpine.DEB.2.20.1703142321360.29558@macbook-air>
On Tue, 14 Mar 2017, Vince Weaver wrote:
> So another obscure rdpmc problem, turned up by the PAPI regression tests.
>
> If you use rdpmc, and your event is attached measuring another process,
> and then you ENABLE/DISABLE/ENABLE/rdpmc the event
>
> somehow the userpg->time_enabled field gets a weird value and that
> completely confuses code expecting enabled!=running to mean multiplexing
> is happening.
Still working on this issue. It turns out it's not rdpmc specific, you
can see it with a regular read() too.
So far I've traced it back far enough to see that shadow_ctx_time is
ending up negative for some reason if you do an enable/disable/enable on
an event attached to another process. I'm trying to trace it back further
but it's a slow process.
Vince
prev parent reply other threads:[~2017-03-17 14:39 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-03-15 3:41 perf: rdpmc mmap page " Vince Weaver
2017-03-17 14:37 ` Vince Weaver [this message]
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=alpine.DEB.2.20.1703171035490.13039@macbook-air \
--to=vincent.weaver@maine.edu \
--cc=acme@kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@redhat.com \
--cc=peterz@infradead.org \
/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
all inboxes | Powered by JetHome®