Re: [PATCH] proc: show readahead state in fdinfo

[Ingo Molnar <mingo@elte.hu>]

* Wu Fengguang <fengguang.wu@intel.com> wrote:

> On Wed, Nov 30, 2011 at 01:57:43AM +0800, Andi Kleen wrote:
> > On Tue, Nov 29, 2011 at 09:09:03PM +0800, Wu Fengguang wrote:
> > > Record the readahead pattern in ra->pattern and extend the ra_submit()
> > > parameters, to be used by the next readahead tracing/stats patches.
> > 
> > I like this, could it be exported it a bit more formally in /proc for 
> > each file descriptor?
> 
> How about this?
> ---
> Subject: proc: show readahead state in fdinfo
> Date: Thu Dec 15 14:35:56 CST 2011
> 
> Append three readahead states to /proc/<PID>/fdinfo/<FD>:

Not a very good idea - please keep debug info under /debug as 
much as possible (as your original series did), instead of 
creating an ad-hoc insta-ABI in /proc.

In the long run we'd really like to retrieve such kind of 
information not even via ad-hoc exported info in /debug but via 
the standard event facilities: the tracepoints, if they are 
versatile enough, could be used to collect these stats and more.

Thanks,

	Ingo

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