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From: Ryan Cumming <bodnar42@phalynx.dhs.org>
To: Jeff Dike <jdike@karaya.com>
Subject: Re: Special Kernel Modification
Date: Sun, 4 Nov 2001 21:30:38 -0800
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On November 4, 2001 21:52, you wrote:
> bodnar42@phalynx.dhs.org said:
> > >  Mounting it synchronous will  disable caching in the VM.
> >
> > Who told
> > you that? Synchronous mounting turns off write buffering. Even with
> > "-o sync" writes will still end up in the page cache, they'll just be
> > commited immediately.
>
> Ummm, how about O_DIRECT instead of O_SYNC (or maybe as well, my googling
> hasn't been clear on whether O_DIRECT bypasses the cache on writes as
> well)?
>

Nope, last I checked O_DIRECT enforces buffer and file offset alignment. 
Normal apps wouldn't work very well at all. Maybe UML needs some hacks around 
the whole caching issue?

-Ryan
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