From: Peter Zijlstra <peterz@infradead.org>
To: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Cc: Ingo Molnar <mingo@redhat.com>,
linux-kernel@vger.kernel.org, Robert Richter <rric@kernel.org>,
Frederic Weisbecker <fweisbec@gmail.com>,
Mike Galbraith <efault@gmx.de>, Paul Mackerras <paulus@samba.org>,
Stephane Eranian <eranian@google.com>,
Andi Kleen <ak@linux.intel.com>
Subject: Re: [RFC v2 2/7] perf: add AUX area to ring buffer for raw data streams
Date: Wed, 25 Jun 2014 14:11:56 +0200 [thread overview]
Message-ID: <20140625121156.GA3935@laptop> (raw)
In-Reply-To: <87lhslxn2s.fsf@ashishki-desk.ger.corp.intel.com>
On Wed, Jun 25, 2014 at 02:09:31PM +0300, Alexander Shishkin wrote:
> Peter Zijlstra <peterz@infradead.org> writes:
>
> > On Wed, Jun 11, 2014 at 06:41:45PM +0300, Alexander Shishkin wrote:
> >> + /*
> >> + * Set up pmu-private data structures for an AUX area
> >> + */
> >> + void *(*setup_aux) (int cpu, void **pages,
> >> + int nr_pages, bool overwrite);
> >> + /* optional */
> >> +
> >> + /*
> >> + * Free pmu-private AUX data structures
> >> + */
> >> + void (*free_aux) (void *aux); /* optional */
> >
> > I was hoping you could replace those with a PERF_CAP_AUX or something
> > and then have one generic allocation routine like you provide in the
> > subsequent patches.
>
> I need these to allocate pmu-specific SG tables now, which I don't see
> how to generalize nicely. User-visible aux_pages are allocated in the
> generic rb_alloc_aux().
>
> As for sg tables, the alternative would be to allocate them in the
> event::pmu::add() path, which is probably not very good for
> performance, unless I'm missing something? Like, I can allocate stuff in
> the first add() and then free it in event::destroy().
>
> Or, we can assume a generic sg table format and allocate them in the
> generic code, but then we'll need more capabilities to indicate at least
> the size of a table entry. PT needs 64 bits per entry, ARM's TMC needs
> 32 and the non-SG PT will still need some tables. But I'd rather leave
> this part to the pmu drivers. What do you think?
Ah, I wasn't aware.. too bad. Maybe add this to the changelog.
next prev parent reply other threads:[~2014-06-25 12:12 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-06-11 15:41 [RFC v2 0/7] perf: perf: add AUX space to ring_buffer Alexander Shishkin
2014-06-11 15:41 ` [RFC v2 1/7] perf: add data_{offset,size} to user_page Alexander Shishkin
2014-06-13 13:51 ` Robert Richter
2014-06-11 15:41 ` [RFC v2 2/7] perf: add AUX area to ring buffer for raw data streams Alexander Shishkin
2014-06-24 17:19 ` Peter Zijlstra
2014-06-25 11:09 ` Alexander Shishkin
2014-06-25 12:11 ` Peter Zijlstra [this message]
2014-06-11 15:41 ` [RFC v2 3/7] perf: support high-order allocations for AUX space Alexander Shishkin
2014-06-11 15:41 ` [RFC v2 4/7] perf: add a capability for AUX_NO_SG pmus to do software double buffering Alexander Shishkin
2014-06-11 15:41 ` [RFC v2 5/7] perf: add a pmu capability for "exclusive" events Alexander Shishkin
2014-06-24 17:18 ` Peter Zijlstra
2014-06-25 11:12 ` Alexander Shishkin
2014-06-11 15:41 ` [RFC v2 6/7] perf: add api for pmus to write to AUX space Alexander Shishkin
2014-06-24 17:27 ` Peter Zijlstra
2014-06-25 11:24 ` Alexander Shishkin
2014-06-25 12:12 ` Peter Zijlstra
2014-06-11 15:41 ` [RFC v2 7/7] perf: add AUX record Alexander Shishkin
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