[OpenAFS-devel] 1.4.8 performance

[Hartmut Reuter]

Jeffrey Hutzelman wrote:
> --On Wednesday, October 08, 2008 12:15:59 PM -0400 Jeffrey Altman 
> <jaltman@secure-endpoints.com> wrote:
> 
>> Hartmut Reuter wrote:
>>
>>>
>>> After integration of my object storage stuff into 1.4.8pre1 I have made
>>> some tests between two of our cell's fileserver machines,
>>> Both Quadcore Intel(R) Xeon(R) CPU           E5405  @ 2.00GHz
>>> with 4 GB main memory. They are both on the same Gbit-Ethernet switch.
>>>
>>> On the client I use 64 MB memory cache with chunk size 64 KB.
>>
>>
>> Why such a small chunk size?
> 
> 
> A good question.  This will adversely affect the transfer rates through 
> the cache manager, because a separate RXAFS_FetchData is done for each 
> chunk. What size reads is afsio doing?  If they're not the same, then 
> the measurements are really not comparable.
> 
> -- Jeff

Normally I use 256 KB, but I think these  64 K are kind of a default 
value. With 64 MB it's not reasonable to use 1 MB chunk size because 
then you would have only 64 chunks at all.

It's true: afsio uses 1MB chunks and is therefore better off here. But 
the big advantage of Matt's bapass cache seems to be the parallelism you 
can get with multi processor machines (On my laptop it's slower than 
normal). The effective transfer size of Matt's code seems to be 128 K, 
but obviously the number of RPCs isn't the problem, but some kind of 
blocking (locking?). Otherwise a simple doubling of throughput is hard 
to explain...

-Hartmut
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Hartmut Reuter                  e-mail 		reuter@rzg.mpg.de
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