linux-kernel - Re: [PATCHv5 0/8] zswap: compressed swap caching

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Message-ID: <512282FF.2050005@linux.vnet.ibm.com>
Date:	Mon, 18 Feb 2013 13:37:35 -0600
From:	Seth Jennings <sjenning@...ux.vnet.ibm.com>
To:	Ric Mason <ric.masonn@...il.com>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Greg Kroah-Hartman <gregkh@...uxfoundation.org>,
	Nitin Gupta <ngupta@...are.org>,
	Minchan Kim <minchan@...nel.org>,
	Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>,
	Dan Magenheimer <dan.magenheimer@...cle.com>,
	Robert Jennings <rcj@...ux.vnet.ibm.com>,
	Jenifer Hopper <jhopper@...ibm.com>,
	Mel Gorman <mgorman@...e.de>,
	Johannes Weiner <jweiner@...hat.com>,
	Rik van Riel <riel@...hat.com>,
	Larry Woodman <lwoodman@...hat.com>,
	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Dave Hansen <dave@...ux.vnet.ibm.com>,
	Joe Perches <joe@...ches.com>, linux-mm@...ck.org,
	linux-kernel@...r.kernel.org, devel@...verdev.osuosl.org
Subject: Re: [PATCHv5 0/8] zswap: compressed swap caching

On 02/15/2013 09:20 PM, Ric Mason wrote:
> On 02/14/2013 02:38 AM, Seth Jennings wrote:
<snip>
>>
>> Some addition performance metrics regarding the performance
>> improvements and I/O reductions that can be achieved using zswap as
>> measured by SPECjbb are provided here:
>>
>> http://ibm.co/VCgHvM
> 
> I see this link.  You mentioned that "When a user enables zswap and
> the hardware accelerator, zswap simply passes the pages to be
> compressed or decompressed off to the accelerator instead of
> performing the work in software". Then how can user enable hardware
> accelerator, there are option in UEFI or ... ?

zswap uses the cryptographic API for accessing compressor modules.  In
the case of Power7+, we have a crypto API driver (crypto/842.c) which
wraps calls to the real driver (drivers/crypto/nx/nx-842.c) which
makes the hardware calls.

To use a compressor module, use the zswap.compressor attribute on the
kernel parameter.  For P7+, for exmaple:

zswap.compressor=842

> 
>> These results include runs on x86 and new results on Power7+ with
>> hardware compression acceleration.

Thanks,
Seth

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