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Date: Thu, 21 Apr 2011 13:50:31 +0800
From: Wu Fengguang <fengguang.wu@intel.com>
To: Christoph Hellwig <hch@infradead.org>
Cc: Andrew Morton <akpm@linux-foundation.org>, Jan Kara <jack@suse.cz>,
        Mel Gorman <mel@linux.vnet.ibm.com>,
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        Itaru Kitayama <kitayama@cl.bb4u.ne.jp>,
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        Linux Memory Management List <linux-mm@kvack.org>
Subject: Re: [PATCH 0/6] writeback: moving expire targets for
 background/kupdate works
Message-ID: <20110421055031.GA23711@localhost>
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 <20110421043449.GA22423@infradead.org>
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Hi Christoph,

On Thu, Apr 21, 2011 at 12:34:50PM +0800, Christoph Hellwig wrote:
> Hi Wu,
> 
> if you're queueing up writeback changes can you look into splitting
> inode_wb_list_lock as it was done in earlier versions of the inode
> scalability patches?  Especially if we don't get the I/O less
> balance_dirty_pages in ASAP it'll at least allows us to scale the
> busy waiting for the list manipulationes to one CPU per BDI.

Do you mean to split inode_wb_list_lock into struct bdi_writeback? 
So as to improve at least the JBOD case now and hopefully benefit the
1-bdi case when switching to multiple bdi_writeback per bdi in future?

I've not touched any locking code before, but it looks like some dumb
code replacement. Let me try it :)

Thanks,
Fengguang