[tor-relays] How effective is "NumCPUs"?

[Andrea Shepard]

On Fri, Jan 24, 2014 at 01:27:54PM -0500, Nick Mathewson wrote:
> So, others have answered pretty well, but I'll add a little too.
> 
> Right now, Tor uses multiple cores to parallelize circuit extension
> handshakes, but not much else.  I'm hoping that in future versions we
> can make serious progress on getting more of our crypto
> parallelized[*] to better take advantage of more cores, but for right
> now, NumCPUs is a good thing, but is not actually adequate for evenly
> dividing your Tor process's CPU load among a larger number of cores.
> 
> [*] See eg discussion at
> https://trac.torproject.org/projects/tor/wiki/org/projects/Tor/MultithreadedCrypto
> .  The design there is still sound, but it needs some C hackers with
> spare time.

The design is solid, and a respectable chunk of it got written, but it took
longer than I thought and I got distracted with other foreground-priority
things at some point, IIRC.  I should rebase it against current master and
get back to it at some point.

-- 
Andrea Shepard
<andrea at torproject.org>
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