linux-ext4 - Re: upcoming kerneloops.org item: get_page_from

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Date:	Thu, 25 Jun 2009 14:05:49 -0700
From:	Joel Becker <Joel.Becker@...cle.com>
To:	Theodore Tso <tytso@....edu>, David Rientjes <rientjes@...gle.com>,
	Andrew Morton <akpm@...ux-foundation.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>,
	penberg@...helsinki.fi, arjan@...radead.org,
	linux-kernel@...r.kernel.org, cl@...ux-foundation.org,
	npiggin@...e.de, linux-ext4@...r.kernel.org
Subject: Re: upcoming kerneloops.org item: get_page_from_freelist

On Thu, Jun 25, 2009 at 04:37:43PM -0400, Theodore Tso wrote:
> Nicely spotted.  Yeah, that's a bug; we need to do something about
> that one, too.  And what we're doing is a bit silly; it may make sense
> to use __get_free_pages if filesystem blocksize == PAGE_SIZE, but
> otherwise we should be using a sub-page allocator.  Right now, we're
> chewing up a 16k PPC page for every 4k filesystem metadata page
> allocated in journal_write_metadata_buffer(), and on x86, for the
> (admittedly uncommon) 1k block filesystem, we'd be chewing up a 4k
> page for a 1k block buffer.
> 
> 
> Both of these problems exist for both ext3 and ext4.

	And ocfs2.

Joel

-- 

Life's Little Instruction Book #337

	"Reread your favorite book."

Joel Becker
Principal Software Developer
Oracle
E-mail: joel.becker@...cle.com
Phone: (650) 506-8127
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