linux-kernel - Re: POSIX_FADV

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Message-Id: <20080814091521.e4d9be53.akpm@linux-foundation.org>
Date:	Thu, 14 Aug 2008 09:15:21 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	"Trevor Woollacott [ MTN - Innovation Centre ]" <Woolla_T@....co.za>
Cc:	<linux-kernel@...r.kernel.org>
Subject: Re: POSIX_FADV_DONTNEED

On Thu, 14 Aug 2008 12:26:28 +0200 "Trevor Woollacott [ MTN - Innovation Centre ]" <Woolla_T@....co.za> wrote:

> 
> > On Fri, 1 Aug 2008 17:05:39 +0200 "Trevor Woollacott [ MTN - Innovation
> > Centre ]" <Woolla_T@....co.za> wrote:

(please don't top-post).

> > > 
> > > Hi all
> > > 
> > > Does anyone know if posix_fadvise() with POSIX_FADV_DONTNEED is
> > > blocking/unblocking?
> > 
> > It tries to be nonblocking and will mostly succeed in that.  It might
> > occasionally block on a metadata read or journal congestion or
> > something, so it isn't guaranteed.
> >
>
> Thanks for the response Andrew. Is there a way to check when the cached
> data has been freed after fadvise has been called?
> 

I assume you meant "whether", not "when".

Not directly.  I believe that the best way of obtaining that
information remains mmap()ing the file then querying the presence of
pages via mincore().
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