[tor-bugs] #24374 [Core Tor/Tor]: Reduce monotime_coarse_absolute_msec() usage

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#24374: Reduce monotime_coarse_absolute_msec() usage
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 Reporter:  ahf                       |          Owner:  nickm
     Type:  enhancement               |         Status:  needs_review
 Priority:  Medium                    |      Milestone:  Tor: 0.3.3.x-final
Component:  Core Tor/Tor              |        Version:
 Severity:  Normal                    |     Resolution:
 Keywords:  s8-perf, review-group-27  |  Actual Points:
Parent ID:  #24062                    |         Points:
 Reviewer:  teor                      |        Sponsor:  Sponsor8
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Changes (by teor):

 * reviewer:   => teor


Comment:

 This compiles and passes make check for me on macOS 10.12, x86_64, Apple
 clang 9.0.0.
 I haven't tested it on i386, because I don't have the libraries installed
 on my local machine.

 I checked that mach_time_info.numer and denom are around the right way.

 The quotient can be up to 40 on PowerPC macs, see:
 https://stackoverflow.com/questions/23378063/how-can-i-use-mach-absolute-
 time-without-overflowing

 I think we are safe from overflow here. And in this context, the divide
 then multiply inaccuracy doesn't matter.

 Next step is to check on i386 and mobile.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/24374#comment:6>
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