network performance

Kris Kennaway kris at
Wed Feb 6 15:08:44 PST 2008

Stefan Lambrev wrote:
> Greetings,
> Kris Kennaway wrote:
>> Stefan Lambrev wrote:
>>>> I'll use again hwpmc and LOCK_PROFILING to see what's going on.
>>>> And will try the same benchmark on quad core processor as now 
>>>> numbers of cores/cpus matter :)
>>> Here are promised results -
> Finally I got pmcstat working -
> The stats are gathered during 600kpp incoming.
> I think that syncache or what calls MD5Transform is not SMP able, and 
> that's why outgoing 250kpps is the limit that I can't beat.

It looks like the syncache is using most of the CPU time.  However you 
are not hitting problems caused by lack of concurrency there.  It does 
do a *lot* of work with the syncache mutex held (including generation of 
the cookie, which involves MD5) so it might be an issue in the future, 
but there are other bottlenecks in the way before that is your main 
issue.  Things may be different with more CPUs.

Did you compare to what happens to performance when the syncache is 


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