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From: Stephen Brennan <stephen.s.brennan@oracle.com>
To: Jiri Olsa <jolsa@redhat.com>
Cc: linux-perf-users@vger.kernel.org
Subject: Re: Perf loses events without reporting
Date: Thu, 01 Jul 2021 10:05:40 -0700	[thread overview]
Message-ID: <87fswyc6cb.fsf@stepbren-lnx.us.oracle.com> (raw)
In-Reply-To: <87im1uc79i.fsf@stepbren-lnx.us.oracle.com>

Stephen Brennan <stephen.s.brennan@oracle.com> writes:
> So hopefully this information helps narrow down the exploration. It
> seems to be Intel PMU specific!

Or more accurately, we only observe it on the Intel systems I've
checked. The AMD systems record fewer cycle events in mdelay() and thus
may not have a chance to skip events. I'll try updating my kernel module
to busy wait by looping until jiffies is above a particular value. This
would hopefully avoid any CPU-specific idling which would reduce the
cycle count on AMD. I'll update this thread with my findings after
testing.

Thanks again,
Stephen

  reply	other threads:[~2021-07-01 17:06 UTC|newest]

Thread overview: 8+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-30 17:29 Perf loses events without reporting Stephen Brennan
2021-07-01 10:37 ` Jiri Olsa
2021-07-01 16:45   ` Stephen Brennan
2021-07-01 17:05     ` Stephen Brennan [this message]
2021-07-01 18:00       ` Stephen Brennan
2021-07-02 16:22         ` Jiri Olsa
2021-07-02 20:12           ` Jiri Olsa
2021-07-02 22:48             ` Stephen Brennan

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