Re: [Gelato-technical] Serious performance degradation on a RAID

[Andreas Hirstius <Andreas.Hirstius@cern.ch>]

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1: Type: text/plain; charset="windows-1252", Size: 1909 bytes --]



Chen, Kenneth W wrote:

>On Tue, Apr 05, 2005 at 09:45:34PM -0700, David Mosberger wrote:
>  
>
>>Did you compile the driver as a module?
>>    
>>
>
>
>Duraid Madina wrote on Tuesday, April 05, 2005 9:53 PM
>  
>
>>Nope. You're not seeing the problem?
>>    
>>
>
>That is the reason for the performance problem.  And this is definitely
>*not* ia64 specific.  See this discussion which started with performance
>problem seen on opteron and reproduced on DELL machine as well.
>http://marc.theaimsgroup.com/?t\x111028927300002&r=1&w=2
>
>The changeset that david pointed out is the right fix.  Or you can just
>take the small patch I posted in the above thread.
>
>  
>

The problems mentioned in this discussion about the Fusion-MPT I can 
perfectly reproduce on my boxes with 2.6.11, but only with pages sizes 
4k and 8k;
With 16k and 64k pages I don't see any problem at all !!!
Actually I see block size <-> page size correlations which are similiar 
to the correlations I see in my setup...
i.e. 2.6.11 and 4k pages:
    dd ...bs@96: 40MB/s
    dd ...bs92: 74MB/s

i.e. 2.6.11 and 8k pages:
    dd ...bs92: 56MB/s
    dd ...bs\x16384: 74MB/s
   
with the driver as module I don't see any change (??).
And I also don't see any change in performance for 4k/8k pages, when 
applying either your small patch or the cset david pointed to...
Since the fusion-mpt driver in 2.6.12-rc2 has this cset applied and no 
other changes, I also don't see improvements with this kernel...
(Again with 16k or 64k pages no performance problem in 2.6.12-rc2 with 
the fusion-mpt driver...)

But the driver in questions is 3w-9xxx and there have been no chances at 
all in this driver between 2.6.10 and 2.6.12-rc1. The changed driver in  
-rc2 still has the problem.
And I've tried the driver built-in and as a module (default)...

Andreas

>- Ken
>
>
>
>  
>