linux-kernel - Re: [PATCH 00/16] raid acceleration and asynchronous offload api for 2.6.22

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Date:	Thu, 10 May 2007 17:32:03 +0200
From:	Tomasz Chmielewski <mangoo@...g.org>
To:	unlisted-recipients:; (no To-header on input)
Cc:	linux-kernel@...r.kernel.org, linux-raid@...r.kernel.org,
	rshitrit@...vell.com, dan.j.williams@...el.com,
	nickpiggin@...oo.com.au, Justin Piszcz <jpiszcz@...idpixels.com>,
	ilmari@...ari.org
Subject: Re: [PATCH 00/16] raid acceleration and asynchronous offload api
 for 2.6.22

Tomasz Chmielewski schrieb:
> Ronen Shitrit wrote:
> 
>> The resync numbers you sent, looks very promising :)
>> Do you have any performance numbers that you can share for these set of
>> patches, which shows the Rd/Wr IO bandwidth.
> 
> I have some simple tests made with hdparm, with the results I don't 
> understand.
> 
> We see hdparm results are fine if we access the whole device:
> 
> thecus:~# hdparm -Tt /dev/sdd
> 
> /dev/sdd:
>  Timing cached reads:   392 MB in  2.00 seconds = 195.71 MB/sec
>  Timing buffered disk reads:  146 MB in  3.01 seconds =  48.47 MB/sec
> 
> 
> But are 10 times worse (Timing buffered disk reads) when we access 
> partitions:

There seems to be another side effect when comparing DMA engine in 
2.6.17-iop1 to 2.6.21-iop1: network performance.

For simple network tests, I use "netperf" tool to measure network 
performance.

With 2.6.17-iop1 and all DMA offloading options enabled (selectable in 
System type ---> IOP3xx Implementation Options  --->), I get nearly 25 
MB/s throughput.

With 2.6.21-iop1 and all DMA offloading optons enabled (moved to Device 
Drivers  ---> DMA Engine support  --->), I get only about 10 MB/s 
throughput.
Additionally, on 2.6.21-iop1, I get lots of "dma_cookie < 0" printed by 
the kernel.

-- 
Tomasz Chmielewski
http://wpkg.org
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