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Message-ID: <20091001072518.GA1502@elte.hu>
Date: Thu, 1 Oct 2009 09:25:18 +0200
From: Ingo Molnar <mingo@...e.hu>
To: Arjan van de Ven <arjan@...radead.org>
Cc: prasad@...ux.vnet.ibm.com, "Frank Ch. Eigler" <fche@...hat.com>,
peterz@...radead.org, linux-kernel@...r.kernel.org,
Frederic Weisbecker <fweisbec@...il.com>
Subject: Re: [RFC PATCH] perf_core: provide a kernel-internal interface to
get to performance counters
* Arjan van de Ven <arjan@...radead.org> wrote:
> On Sun, 27 Sep 2009 00:02:46 +0530
> "K.Prasad" <prasad@...ux.vnet.ibm.com> wrote:
>
> > On Sat, Sep 26, 2009 at 12:03:28PM -0400, Frank Ch. Eigler wrote:
>
> > > For what it's worth, this sort of thing also looks useful from
> > > systemtap's point of view.
> >
> > Wouldn't SystemTap be another user that desires support for
> > multiple/all CPU perf-counters (apart from hw-breakpoints as a
> > potential user)? As Arjan pointed out, perf's present design would
> > support only a per-CPU or per-task counter; not both.
>
> I'm sorry but I think I am missing your point. "all cpu counters"
> would be one small helper wrapper away, a helper I'm sure the
> SystemTap people are happy to submit as part of their patch series
> when they submit SystemTap to the kernel.
Yes, and Frederic wrote that wrapper already for the hw-breakpoints
patches. It's a non-issue and does not affect the design - we can always
gang up an array of per cpu perf events, it's a straightforward use of
the existing design.
User-space tools have been doing this for ages already, 'perf top' will
open an array of per cpu events to monitor all events in the system.
Ingo
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