[tor-bugs] #25269 [Core Tor/Tor]: Set codegen-units to 1 in src/rust/Cargo.toml to eke out every last drop of performance

[Tor Bug Tracker & Wiki]

#25269: Set codegen-units to 1 in src/rust/Cargo.toml to eke out every last drop of
performance
-------------------------------------------------+-------------------------
 Reporter:  cypherpunks                          |          Owner:
                                                 |  Backxwash
     Type:  enhancement                          |         Status:
                                                 |  needs_information
 Priority:  Medium                               |      Milestone:  Tor:
                                                 |  0.3.5.x-final
Component:  Core Tor/Tor                         |        Version:
 Severity:  Normal                               |     Resolution:
 Keywords:  rust, easy, 034-triage-20180328,     |  Actual Points:
  034-removed-20180328, fast-fix                 |
Parent ID:                                       |         Points:  .1
 Reviewer:  nickm                                |        Sponsor:
-------------------------------------------------+-------------------------

Comment (by isis):

 Totally hand-wavey measurement in a Qubes VM on a x220 with an i5 using
 turboboost doing like a million other things, running `configure --enable-
 rust --enable-cargo-online-mode --enable-fatal-warnings --disable-asciidoc
 && time make -j4`:

 With `codegen-units = 1`:

 {{{
 real    5m15.728s
 user    14m29.903s
 sys     3m55.476s
 }}}

 Without:

 {{{
 real    5m18.433s
 user    15m15.399s
 sys     4m12.781s
 }}}

 So it seems to have a negligible effect on build times if it randomly
 ended up being longer without it? I don't know how much faster it makes
 the binaries.

--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/25269#comment:14>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online