linux-kernel - Re: Is nobh code still useful?

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Message-ID: <20090918162554.13a72664@infradead.org>
Date:	Fri, 18 Sep 2009 16:25:54 +0200
From:	Arjan van de Ven <arjan@...radead.org>
To:	Theodore Tso <tytso@....edu>
Cc:	Badari Pulavarty <pbadari@...ibm.com>, Jan Kara <jack@...e.cz>,
	linux-fsdevel@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
	Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: Is nobh code still useful?

On Fri, 18 Sep 2009 10:12:26 -0400
Theodore Tso <tytso@....edu> wrote:

> On Thu, Sep 17, 2009 at 09:21:37PM -0700, Badari Pulavarty wrote:
> >
> > Originally it was supported on ext2. I added support nobh support
> > for ext3. At that time, the main
> > issue/complaint was that, these bufferheads consume memory from  
> > ZONE_NORMAL causing
> > memory pressure on 32-bit (i386) configurations.
> 
> Specifically, it matters on very large configuration systems (i.e.,
> 32GB-64GB using PAE-36) that today we'd probably just say, "use
> x86_64, you moron".  It would probably matter if someone were to want
> to upgrade a non-64-bit capable machine to a newer kernel.  
> 
> Dropping nobh from ext3 at this point might prevent some of these
> older systems from upgrading, I'm not sure how much we would care; on
> the one hand, these machines tended to be pretty expensive, so people
> would probably want to use them for a while.  On the other hand, it
> has been over five years now since x86_64 machines have been
> available, and many of these customers are highly unlikely to want to
> upgrade anyway.

isn't the converse to just make nobh the default but not an option a
better approach then?
I forgot why this was a good idea to be an option again ;-)



-- 
Arjan van de Ven 	Intel Open Source Technology Centre
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