Date: Thu, 31 Jul 2003 15:32:11 -0700
From: Andrew Morton <akpm@osdl.org>
To: "Muthian S" <muthian_s@hotmail.com>
Cc: linux-kernel@vger.kernel.org
Subject: Re: madvise on file pages
Message-Id: <20030731153211.16c9ccb3.akpm@osdl.org>
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"Muthian S" <muthian_s@hotmail.com> wrote:
>
> Hi,
> 
> Could someone inform as to what is the behavior when madvise DONTNEED is 
> called on pages that are mmap'd from local files mapped with MAP_SHARED, 
> i.e. they share the same page that the file cache does.

The pages are unmapped from the calling process's pagetables.  We don't
actually free the physical pages.

> In such cases, can 
> madvise be made to release specific pages in the file cache by mmap-ing the 
> relevant file segment ?

No.

2.6 kernels implement the fadvise() syscall (accessible by glibc's
posix_fadvise() function) which will do this.

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