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Date: Tue, 19 Nov 2013 14:13:04 +0100
From: Ingo Molnar <mingo@kernel.org>
To: Peter Zijlstra <peterz@infradead.org>
Cc: David Ahern <dsahern@gmail.com>, Namhyung Kim <namhyung@kernel.org>,
        Arnaldo Carvalho de Melo <acme@ghostprotocols.net>,
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        Frederic Weisbecker <fweisbec@gmail.com>,
        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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* Peter Zijlstra <peterz@infradead.org> wrote:

> On Tue, Nov 19, 2013 at 12:48:10PM +0100, Peter Zijlstra wrote:
> > And that does indeed seem to side-step the perf sw pagefault event, but
> > that is arguably a perf bug.
> 
> To clarify; mm/memory.c:handle_mm_fault() is where the VM counts its 
> generic PGFAULT event, but our perf sw event is in the arch fault 
> handler.
> 
> So they count different but related things.

I think that assymetry was intended: we didn't want to count 
'synchronous' pagefaults like get_user_pages() or mlock() bringing in 
pages, only asynchronous/real ones, or so.

Thanks,

	Ingo