linux-kernel - Re: [PATCH] JBD slab cleanups

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Date:	Mon, 17 Sep 2007 15:01:06 -0700
From:	Badari Pulavarty <pbadari@...ibm.com>
To:	cmm@...ibm.com
Cc:	Christoph Hellwig <hch@...radead.org>,
	Christoph Lameter <clameter@....com>,
	linux-fsdevel <linux-fsdevel@...r.kernel.org>,
	ext4 development <linux-ext4@...r.kernel.org>,
	lkml <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] JBD slab cleanups

On Mon, 2007-09-17 at 12:29 -0700, Mingming Cao wrote:
> On Fri, 2007-09-14 at 11:53 -0700, Mingming Cao wrote:
> > jbd/jbd2: Replace slab allocations with page cache allocations
> > 
> > From: Christoph Lameter <clameter@....com>
> > 
> > JBD should not pass slab pages down to the block layer.
> > Use page allocator pages instead. This will also prepare
> > JBD for the large blocksize patchset.
> > 
> 
> Currently memory allocation for committed_data(and frozen_buffer) for
> bufferhead is done through jbd slab management, as Christoph Hellwig
> pointed out that this is broken as jbd should not pass slab pages down
> to IO layer. and suggested to use get_free_pages() directly.
> 
> The problem with this patch, as Andreas Dilger pointed today in ext4
> interlock call, for 1k,2k block size ext2/3/4, get_free_pages() waste
> 1/3-1/2 page space. 
> 
> What was the originally intention to set up slabs for committed_data(and
> frozen_buffer) in JBD? Why not using kmalloc?
> 
> Mingming

Looks good. Small suggestion is to get rid of all kmalloc() usages and
consistently use jbd_kmalloc() or jbd2_kmalloc().

Thanks,
Badari

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