[distcc] homogeneous environments

Robert W. Anderson anderson110 at poptop.llnl.gov
Tue May 5 16:37:27 GMT 2009


Fergus Henderson wrote:
> 
> 
> On Thu, Apr 30, 2009 at 9:07 PM, Robert W. Anderson 
> <anderson110 at poptop.llnl.gov <mailto:anderson110 at poptop.llnl.gov>> wrote:
> 
>     Fergus Henderson wrote:
> 
>         The include server could be the bottleneck.  What's the CPU
>         usage for the include server process?
>         Or it could be disk I/O.  Try iostat or vmstat to profile that.
> 
> 
>     After some more experimentation, I think I may have a clue what's
>     going on here.  I think I may be getting bound up in context
>     switching costs, both in my single node performance and on localhost
>     using distcc.
> 
>     On a single node:
> 
>     -j4: 24 million context switches @ 10us = 4m
>     -j8: 96 million context switches @ 10us = 16m
>     ...
> 
>     I don't understand why doubling the job count increases context
>     switching by 4x.  Any insights appreciated.
> 
> 
> You mentioned earlier that your host has four processors.

No, I mentioned a few times that it has 16 processors.

Thanks,
-- 
Robert W. Anderson
Center for Applied Scientific Computing
Email: anderson110 at llnl.gov
Tel: 925-424-2858  Fax: 925-423-8704


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