linux-kernel - Re: [PATCH 7/7] zram/xvmalloc: combine duplicate block delete code

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Message-ID: <4D46B9A9.1060205@vflare.org>
Date:	Mon, 31 Jan 2011 08:31:21 -0500
From:	Nitin Gupta <ngupta@...are.org>
To:	Greg Kroah-Hartman <gregkh@...e.de>,
	Pekka Enberg <penberg@...helsinki.fi>,
	devel@...verdev.osuosl.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 7/7] zram/xvmalloc: combine duplicate block delete code

On 01/28/2011 10:01 AM, Robert Jennings wrote:
> This patch eliminates duplicate code.  The remove_block_head function
> is a special case of remove_block which can be contained in remove_block
> without confusion.
>
> The portion of code in remove_block_head which was noted as "DEBUG ONLY"
> is now mandatory.  Doing this provides consistent management of the double
> linked list of blocks under a freelist and makes this consolidation
> of delete block code safe.  The first and last blocks will have NULL
> pointers in their previous and next page pointers respectively.
>
> Additionally, any time a block is removed from a free list the next and
> previous pointers will be set to NULL to avoid misuse outside xvmalloc.
>
> Signed-off-by: Robert Jennings<rcj@...ux.vnet.ibm.com>

The reason for introducing remove_block_head() as a separate function 
was to make malloc slightly faster but since I lack any profiling data, 
I'm not very sure if this may impact performance. Ideally, some sort of 
data with some malloc heavy test would have been useful. Anyways, I 
think major allocator changes will happen when we make xvmalloc 
allocated memory reclaimable, so maybe we can defer profiling.

Acked-by: Nitin Gupta <ngupta@...are.org>

Thanks,
Nitin
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