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Subject: Re: [RFC] Tracer Ring Buffer splice() vs page cache [was: Re: Perf
 and ftrace [was Re: PyTimechart]]
From: Peter Zijlstra <peterz@infradead.org>
To: Mathieu Desnoyers <mathieu.desnoyers@efficios.com>
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       Christoph Lameter <cl@linux-foundation.org>, Tejun Heo <tj@kernel.org>,
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Date: Tue, 18 May 2010 17:23:53 +0200
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On Tue, 2010-05-18 at 11:16 -0400, Mathieu Desnoyers wrote:
> > Also, suppose it was still in the page-cache and still dirty, a steal()
> > would then punch a hole in the file.
> 
> page_cache_pipe_buf_steal starts by doing a wait_on_page_writeback(page); and
> then does a try_to_release_page(page, GFP_KERNEL). Only if that succeeds is the
> action of stealing succeeding. 

If you're going to wait for writeback I don't really see the advantage
of stealing over simply allocating a new page.