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Message-ID: <4B16E727.9070104@kernel.org>
Date:	Thu, 03 Dec 2009 07:16:07 +0900
From:	Tejun Heo <tj@...nel.org>
To:	Christoph Lameter <cl@...ux-foundation.org>
CC:	Ingo Molnar <mingo@...e.hu>,
	Stephen Rothwell <sfr@...b.auug.org.au>,
	michal.simek@...alogix.com, linux-next@...r.kernel.org,
	LKML <linux-kernel@...r.kernel.org>,
	Rusty Russell <rusty@...tcorp.com.au>
Subject: Re: problems in linux-next (Was: Re: linux-next: Tree for December
 1)
On 12/02/2009 11:55 PM, Christoph Lameter wrote:
> On Wed, 2 Dec 2009, Tejun Heo wrote:
> 
>> This isn't usual alignment.  struct work_struct has one data fields
>> which is overloaded for two purposes.  Lower few bits are used to
>> carry flags while upper bits are used to point to sruct
>> cpu_workqueue_struct.  So, the number of available bits for flags are
>> determined by the alignment of cpu_workqueue_struct.  Memory usage for
> 
> The default mininum slab alignment in UP is 8 bytes which means you can
> use 3 bits. And as far as I can see only the lower two bits are used. You
> still have one bit leftover. (current upstream that is did not check if
> you modified it).
For colored workqueue flushing, it ends up using more than three bits.
I haven't decided it fully yet but total of six or seven depending on
how many colors are used.  So, we need forced alignment anyway.
Thanks.
-- 
tejun
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