Re: [Xen-devel] [PATCH RFC 04/23] libxc: add support for FreeBSD

[Ian Campbell <Ian.Campbell@xxxxxxxxxx>]

On Thu, 2014-04-17 at 17:30 +0100, Ian Jackson wrote:
> > +    /* Discard from the buffer cache. */
> > +    if ( posix_fadvise(fd, 0, cur, POSIX_FADV_DONTNEED) < 0 )
> > +        goto out;
> 
> Which also means that the use of posix_fadvise is hardly safe.
> fadvise can quite legally be a noop.

I think that's ok, it's for "reducing the impact on dom0" not
correctness, according to the commit which added it:

commit e0b421d24279d3cce426c0df4bf6d8734c6ce325
Author: Keir Fraser <keir@xxxxxxxxxxxxx>
Date:   Sat Feb 24 14:48:17 2007 +0000

    Reduce impact of saving/restoring/dumping large domains on Dom0 memory
    usage by means of fadvise64() to tell the OS to discard the cache
    pages used for the save/dump file.
    
    Signed-off-by: Simon Graham <Simon.Graham@xxxxxxxxxxx>

(I presume fadvise implemented as a nop should still return success)

Ian.


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