From: Peter Zijlstra <peterz@infradead.org>
To: Andi Kleen <andi@firstfloor.org>
Cc: Taylor Andrews <andrewst@vmware.com>,
"linux-perf-users@vger.kernel.org"
<linux-perf-users@vger.kernel.org>
Subject: Re: Question about Perf's handling of in-use performance counters
Date: Fri, 28 Oct 2016 18:28:44 +0200 [thread overview]
Message-ID: <20161028162844.GJ3142@twins.programming.kicks-ass.net> (raw)
In-Reply-To: <20161028154012.GC26852@two.firstfloor.org>
On Fri, Oct 28, 2016 at 08:40:12AM -0700, Andi Kleen wrote:
> > No, it was about the (mis)guide-line having fundamental races and the
> > belief that the BIOS has no business what so ever using these resources
> > to begin with.
>
> In this case it's not the BIOS, but a hypervisor who allocates the
> counter. I believe there are valid use cases here.
>
> The same issue can also happen when people use user space perfmon
> tools, like PCM or likwid, and potentially with other non BIOS users.
User space writing of the MSRs is not supported and people who do this
get to keep all pieces.
But the thing is still racy, and therefore useless.
next prev parent reply other threads:[~2016-10-28 16:28 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-10-21 21:59 Question about Perf's handling of in-use performance counters Taylor Andrews
2016-10-27 18:11 ` Andi Kleen
2016-10-27 21:00 ` Peter Zijlstra
2016-10-28 13:53 ` Andi Kleen
2016-10-28 14:03 ` Peter Zijlstra
2016-10-28 15:40 ` Andi Kleen
2016-10-28 16:28 ` Peter Zijlstra [this message]
2016-10-28 16:33 ` Andi Kleen
2016-10-28 18:28 ` Taylor Andrews
2016-11-30 15:44 ` Taylor Andrews
2016-11-30 18:17 ` Peter Zijlstra
2016-11-07 22:25 ` Taylor Andrews
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