linux-kernel - Re: [PATCH v2 0/3] staging: zcache: xcfmalloc support

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Date:	Thu, 29 Sep 2011 12:47:28 -0500
From:	Seth Jennings <sjenning@...ux.vnet.ibm.com>
To:	Seth Jennings <sjenning@...ux.vnet.ibm.com>
CC:	gregkh@...e.de, dan.magenheimer@...cle.com, ngupta@...are.org,
	cascardo@...oscopio.com, devel@...verdev.osuosl.org,
	linux-kernel@...r.kernel.org, rdunlap@...otime.net,
	linux-mm@...ck.org, rcj@...ux.vnet.ibm.com,
	dave@...ux.vnet.ibm.com, brking@...ux.vnet.ibm.com
Subject: Re: [PATCH v2 0/3] staging: zcache: xcfmalloc support

On 09/07/2011 09:09 AM, Seth Jennings wrote:
> 
> I did some quick tests with "time" using the same program and the
> timings are very close (3 run average, little deviation):
> 
> xvmalloc:
> zero filled	0m0.852s
> text (75%)	0m14.415s
> 
> xcfmalloc:
> zero filled	0m0.870s
> text (75%)	0m15.089s
> 
> I suspect that the small decrease in throughput is due to the
> extra memcpy in xcfmalloc.  However, these timing, more than 
> anything, demonstrate that the throughput is GREATLY effected
> by the compressibility of the data.

This is not correct.  I found out today that the reason text
compressed so much more slowly is because my test program
was inefficiently filling text filled pages.

With my corrected test program:
xvmalloc:
zero filled	0m0.751s
text (75%)	0m2.273s

It is still slower on less compressible data but not to the
degree previously stated.

I don't have the xcfmalloc numbers yet, but I expect they are
almost the same.

--
Seth

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