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Subject: Re: Patch workqueue: create new slab cache instead of hacking
From: Eric Dumazet <eric.dumazet@gmail.com>
To: Christoph Lameter <cl@linux.com>
Cc: Tejun Heo <tj@kernel.org>, Lai Jiangshan <laijs@cn.fujitsu.com>,
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Date: Wed, 21 Mar 2012 07:49:41 -0700
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On Wed, 2012-03-21 at 09:12 -0500, Christoph Lameter wrote:
> How about this instead?
> 
> Subject: workqueues: Use new kmem cache to get aligned memory for workqueues
> 
> The workqueue logic currently improvises by doing a kmalloc allocation and
> then aligning the object. Create a slab cache for that purpose with the
> proper alignment instead.
> 
> Cleans up the code and makes things much simpler. No need anymore to carry
> an additional pointer to the beginning of the kmalloc object.
> 
> Signed-off-by: Christoph Lameter <cl@linux.com>

Creating a dedicated cache for few objects ? Thats a lot of overhead, at
least for SLAB (no merges of caches)

By the way network stack also wants to align struct net_device (in
function alloc_netdev_mqs(), and uses a custom code.

In this case, as the size of net_device is not constant, we use standard
kzalloc().

No idea why NETDEV_ALIGN is 32 ... Oh well, some old constant instead of
L1_CACHE_BYTES ...