From: Peter Zijlstra <peterz@infradead.org>
To: "Liang, Kan" <kan.liang@linux.intel.com>
Cc: mingo@redhat.com, linux-kernel@vger.kernel.org, acme@kernel.org,
tglx@linutronix.de, jolsa@redhat.com, eranian@google.com,
ak@linux.intel.com
Subject: Re: [PATCH V3 1/5] perf/x86/intel: fix event update for auto-reload
Date: Sat, 10 Feb 2018 15:09:10 +0100 [thread overview]
Message-ID: <20180210140910.GQ25201@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <cafc7994-bb39-14a3-ad20-1357d688a7ff@linux.intel.com>
On Fri, Feb 09, 2018 at 10:49:35AM -0500, Liang, Kan wrote:
>
>
> On 2/9/2018 9:09 AM, Peter Zijlstra wrote:
> > On Tue, Feb 06, 2018 at 12:58:23PM -0500, Liang, Kan wrote:
> > >
> > >
> > > > With the exception of handling 'empty' buffers, I ended up with the
> > > > below. Please try again.
> > > >
> > >
> > > There are two small errors. After fixing them, the patch works well.
> >
> > Well, it still doesn't do A, two read()s without PEBS record in between.
> > So that needs fixing. What 3/5 does, call x86_perf_event_update() after
> > drain_pebs() is actively wrong after this patch.
> >
>
> As my understanding, for case A, drain_pebs() will return immediately. It
> cannot reach the patch.
> Because there is no PEBS record ready. So the ds->pebs_index should be the
> same as ds->pebs_buffer_base.
Right, so fix that.
> 3/5 is to handle case A.
3/5 is terminatlly broken, you should not call x86_perf_event_update()
on a auto-reload event _ever_ after my patch.
next prev parent reply other threads:[~2018-02-10 14:09 UTC|newest]
Thread overview: 26+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-01-29 16:29 [PATCH V3 0/5] bugs fix for large PEBS mmap read and rdpmc read kan.liang
2018-01-29 16:29 ` [PATCH V3 1/5] perf/x86/intel: fix event update for auto-reload kan.liang
2018-02-06 15:06 ` Peter Zijlstra
2018-02-06 17:58 ` Liang, Kan
2018-02-09 14:09 ` Peter Zijlstra
2018-02-09 15:49 ` Liang, Kan
2018-02-10 14:09 ` Peter Zijlstra [this message]
2018-01-29 16:29 ` [PATCH V3 2/5] perf/x86: introduce read function for x86_pmu kan.liang
2018-01-29 16:29 ` [PATCH V3 3/5] perf/x86/intel/ds: introduce read function for large pebs kan.liang
2018-01-29 16:29 ` [PATCH V3 4/5] perf/x86/intel: fix pmu read for large PEBS kan.liang
2018-01-29 16:29 ` [PATCH V3 5/5] perf/x86: fix: disable userspace RDPMC usage " kan.liang
2018-01-30 9:16 ` [PATCH V3 0/5] bugs fix for large PEBS mmap read and rdpmc read Stephane Eranian
2018-01-30 13:39 ` Jiri Olsa
2018-01-30 14:59 ` Liang, Kan
2018-01-30 15:04 ` Jiri Olsa
2018-01-30 15:25 ` Liang, Kan
2018-01-30 16:36 ` Stephane Eranian
2018-01-30 16:48 ` Liang, Kan
2018-01-30 18:52 ` Jiri Olsa
2018-01-30 19:56 ` Stephane Eranian
2018-01-31 3:59 ` Andi Kleen
2018-01-31 9:15 ` Jiri Olsa
2018-01-31 13:15 ` Jiri Olsa
2018-01-31 15:15 ` Liang, Kan
2018-01-31 15:41 ` Jiri Olsa
2018-01-30 14:41 ` Liang, Kan
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