[tor-bugs] #1749 [Core Tor/Tor]: Split relay and link crypto across multiple CPU cores

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#1749: Split relay and link crypto across multiple CPU cores
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 Reporter:  nickm                                |          Owner:  nickm
     Type:  project                              |         Status:
                                                 |  accepted
 Priority:  High                                 |      Milestone:  Tor:
                                                 |  unspecified
Component:  Core Tor/Tor                         |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  tor-relay, term-project-ideas,       |  Actual Points:
  threads, performance                           |
Parent ID:                                       |         Points:  10
 Reviewer:                                       |        Sponsor:
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Comment (by chelseakomlo):

 Replying to [comment:16 nickm]:
 > Replying to [comment:14 chelseakomlo]:
 > > How likely is it that this functionality (or parts of it) can be
 implemented in Rust? Would it require a lot of refactoring or is it
 already fairly modularized?
 >
 > It's not so well modularized right now.  The big problem here is that
 the code is written with the assjumption that relay crypto finishes
 immediately, but with this change, we'd sometimes have to wait on another
 thread before we had cells to send on a given circuit.

 Ok, understood- it seems like `relay_crypt_one_payload` is the place where
 this would happen, and instead of blocking, it would emit an event once
 the relay crypto finishes.

 I'll dig more into
 https://trac.torproject.org/projects/tor/wiki/org/projects/Tor/MultithreadedCrypto,
 and will come up with a mini implementation plan for review.

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Ticket URL: <https://trac.torproject.org/projects/tor/ticket/1749#comment:17>
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