linux-kernel - Re: [PATCH] perf/x86: Reject non sampling events with precise

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Message-ID: <alpine.DEB.2.11.1701031704140.3940@pianoman.cluster.toy>
Date:   Tue, 3 Jan 2017 17:06:41 -0500 (EST)
From:   Vince Weaver <vince@...ter.net>
To:     Jiri Olsa <jolsa@...hat.com>
cc:     Peter Zijlstra <peterz@...radead.org>,
        Jiri Olsa <jolsa@...nel.org>,
        lkml <linux-kernel@...r.kernel.org>,
        Ingo Molnar <mingo@...nel.org>,
        Andi Kleen <andi@...stfloor.org>,
        Alexander Shishkin <alexander.shishkin@...ux.intel.com>,
        Arnaldo Carvalho de Melo <acme@...nel.org>
Subject: Re: [PATCH] perf/x86: Reject non sampling events with precise_ip

On Tue, 3 Jan 2017, Jiri Olsa wrote:
> On Tue, Jan 03, 2017 at 10:40:59AM +0100, Peter Zijlstra wrote:
> > 
> > I think we should reject non sampling pebs events, as you say they make
> > no sense what so ever.
> 
> ook, attached
> 

you can use the PEBS events to gather aggregate stats though and they 
seem roughly right.  Are they truly meaningless?

I had misremembered that they might not have the determinism problems of 
regular events (turns out that's wrong).  They oddly seem to be worse in 
some limited tests I did.

So I guess nothing will be lost if they're disabled.

Vince