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From: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
To: Lee Schermerhorn <Lee.Schermerhorn@hp.com>
Subject: Re: [PATCH] Add tracepoints to track pagecache transition
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Date: Fri, 20 Feb 2009 10:13:37 +0900 (JST)
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Hi

> > > Currently, we can understand the amount of pagecache from "Cached"
> > > in /proc/meminfo. So I'd like to understand which files are using pagecache.
> > 
> > There is one meta question, Why do you think file-by-file pagecache
> > infomartion is valueable?
> 
> One might take a look at Marcello Tosatti's old 'vmtrace' patch.  It
> contains it's own data store/transport via relayfs, but the trace points
> could be ported to the current kernel tracing infrastructure.
> 
> Here's a starting point:   http://linux-mm.org/VmTrace
> 
> Quoting from that page:
> 
> >From the previous email to linux-mm:
> >"The sequence of pages which a given process or workload accesses
> >during its lifetime, a.k.a. "reference trace", is very important
> >information. It has been used in the past for comparison of page
> >replacement algorithms and other optimizations..."

Sure.
but strong difference exist.

vmtrace
  - can run standalone
  - reviewer can confirm its output result is useful or not.

Christoph also explained reason more kindly.
I think we need useful consumer.