linux-kernel - Re: [patch] tracing/mm: add page frame snapshot trace

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Date:	Sat, 9 May 2009 12:27:51 +0200
From:	Ingo Molnar <mingo@...e.hu>
To:	Wu Fengguang <fengguang.wu@...el.com>
Cc:	Frédéric Weisbecker <fweisbec@...il.com>,
	Steven Rostedt <rostedt@...dmis.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Li Zefan <lizf@...fujitsu.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>,
	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>,
	Andi Kleen <andi@...stfloor.org>,
	Matt Mackall <mpm@...enic.com>,
	Alexey Dobriyan <adobriyan@...il.com>,
	"linux-mm@...ck.org" <linux-mm@...ck.org>
Subject: Re: [patch] tracing/mm: add page frame snapshot trace


* Ingo Molnar <mingo@...e.hu> wrote:

> * Wu Fengguang <fengguang.wu@...el.com> wrote:
> 
> > 2) support concurrent object iterations
> >    For example, a huge 1TB memory space can be split up into 10
> >    segments which can be queried concurrently (with different options).
> 
> this should already be possible. If you lseek the trigger file, 
> that will be understood as an 'offset' by the patch, and then 
> write a (decimal) value into the file, that will be the count.
> 
> So it should already be possible to fork off nr_cpus helper 
> threads, one bound to each CPU, each triggering trace output of a 
> separate segment of the memory map - and each reading that CPU's 
> trace_pipe_raw file to recover the data - all in parallel.

And note that trace_pipe_raw supports splice(), while 
/proc/{kpageflags|kpagecount} does not, so the output side might 
probably be a bit faster than the /proc method.

	Ingo
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