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Date: Wed, 13 Nov 2013 13:16:17 +0100
From: Peter Zijlstra <peterz@infradead.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: David Ahern <dsahern@gmail.com>,
        Arnaldo Carvalho de Melo <acme@ghostprotocols.net>,
        linux-kernel@vger.kernel.org, jolsa@redhat.com,
        Frederic Weisbecker <fweisbec@gmail.com>,
        Namhyung Kim <namhyung@kernel.org>, Mike Galbraith <efault@gmx.de>,
        Stephane Eranian <eranian@google.com>
Subject: Re: [PATCH 4/5] perf record: mmap output file - v5
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On Wed, Nov 13, 2013 at 12:50:21PM +0100, Ingo Molnar wrote:
> 
> * Peter Zijlstra <peterz@infradead.org> wrote:
> 
> > On Tue, Nov 12, 2013 at 10:11:21PM +0100, Ingo Molnar wrote:
> > > 
> > > * David Ahern <dsahern@gmail.com> wrote:
> > > 
> > > > > Dunno.. it _should_ all work. Try it and see what it does.. Once the 
> > > > > events are bigger than a page things might get 'interesting' though.
> > > 
> > > Which could be the case with call-graph recording, right?
> > 
> > Not typically, I think we're limiting call graphs to 127 u64, which is 
> > ~1k. Maybe you can blow the single page if you also do a large 
> > top-of-stack copy for dwarf/unwind nonsense.
> 
> What I meant was dwarf style call graph recording:

Ah, one of those things I've never yet used ;-)

>  tools/perf/builtin-record.c:                    const unsigned long default_stack_dump_size = 8192;
> 
> Doesn't that mean 8K+ events?

Oh yes.. that's ideal to trigger this.