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Austin Clements 89b7a08aea runtime: fix gctrace STW CPU time and CPU fraction
The CPU time reported in the gctrace for STW phases is simply
work.stwprocs times the wall-clock duration of these phases. However,
work.stwprocs is set to gcprocs(), which is wrong for multiple
reasons:

1. gcprocs is intended to limit the number of Ms used for mark
   termination based on how well the garbage collector actually
   scales, but the gctrace wants to report how much CPU time is being
   stolen from the application. During STW, that's *all* of the CPU,
   regardless of how many the garbage collector can actually use.

2. gcprocs assumes it's being called during STW, so it limits its
   result to sched.nmidle+1. However, we're not calling it during STW,
   so sched.nmidle is typically quite small, even if GOMAXPROCS is
   quite large.

Fix this by setting work.stwprocs to min(ncpu, GOMAXPROCS). This also
fixes the overall GC CPU fraction, which is based on the computed CPU
times.

Fixes #22725.

Change-Id: I64b5ce87e28dbec6870aa068ce7aecdd28c058d1
Reviewed-on: https://go-review.googlesource.com/77710
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rick Hudson <rlh@golang.org>
2017-11-15 18:23:23 +00:00
.github doc: add a link to the code of conduct 2017-11-13 16:48:04 +00:00
api api: update next.txt 2017-10-28 00:00:56 +00:00
doc doc: correct supported gdb version info 2017-11-14 21:05:02 +00:00
lib/time time: vendor tzdata-2017b and update test 2017-06-07 21:23:58 +00:00
misc cmd/cgo: permit passing string values directly between Go and C 2017-11-15 03:36:54 +00:00
src runtime: fix gctrace STW CPU time and CPU fraction 2017-11-15 18:23:23 +00:00
test cmd/compile: add test for array decomposition 2017-11-13 20:22:22 +00:00
.gitattributes
.gitignore .gitignore: ignore src/cmd/dist/dist 2017-10-28 21:55:49 +00:00
AUTHORS A+C: final updates for Go 1.9 2017-07-18 01:47:54 +00:00
CONTRIBUTING.md .github: recommend 'go bug' when filing an issue 2017-07-24 17:18:34 +00:00
CONTRIBUTORS A+C: final updates for Go 1.9 2017-07-18 01:47:54 +00:00
favicon.ico website: recreate 16px and 32px favicon 2016-08-25 15:43:32 +00:00
LICENSE doc: revert copyright date to 2009 2016-06-01 22:40:04 +00:00
PATENTS
README.md readme: add attribution for the Gopher image 2017-02-03 19:39:41 +00:00
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