delta/go-git.git/src/runtime/debug.go, branch dev.go2go

runtime: update docs for GOMAXPROCS

2020-09-10T14:44:25+00:00

https://github.com/golang/go/blob/master/doc/effective_go.html#L3211 is used to update the docs comment for `GOMAXPROCS` function.

Fixes #41275

Change-Id: I39f58e93a267c6e9f3ac6638ed51acbe5284ada2
GitHub-Last-Rev: e45c8ac5873979397d747838fd8d41e252aec489
GitHub-Pull-Request: golang/go#41276
Reviewed-on: https://go-review.googlesource.com/c/go/+/253537
Reviewed-by: Keith Randall

runtime: don't hold worldsema across mark phase

2020-03-18T19:13:50+00:00

This change makes it so that worldsema isn't held across the mark phase.
This means that various operations like ReadMemStats may now stop the
world during the mark phase, reducing latency on such operations.

Only three such operations are still no longer allowed to occur during
marking: GOMAXPROCS, StartTrace, and StopTrace.

For the former it's because any change to GOMAXPROCS impacts GC mark
background worker scheduling and the details there are tricky.

For the latter two it's because tracing needs to observe consistent GC
start and GC end events, and if StartTrace or StopTrace may stop the
world during marking, then it's possible for it to see a GC end event
without a start or GC start event without an end, respectively.

To ensure that GOMAXPROCS and StartTrace/StopTrace cannot proceed until
marking is complete, the runtime now holds a new semaphore, gcsema,
across the mark phase just like it used to with worldsema.

This change is being landed once more after being reverted in the Go
1.14 release cycle, since CL 215157 allows it to have a positive
effect on system performance.

For the benchmark BenchmarkReadMemStatsLatency in the runtime, which
measures ReadMemStats latencies while the GC is exercised, the tail of
these latencies reduced dramatically on an 8-core machine:

name                   old 50%tile-ns  new 50%tile-ns  delta
ReadMemStatsLatency-8      4.40M ±74%      0.12M ± 2%  -97.35%  (p=0.008 n=5+5)

name                   old 90%tile-ns  new 90%tile-ns  delta
ReadMemStatsLatency-8       102M ± 6%         0M ±14%  -99.79%  (p=0.008 n=5+5)

name                   old 99%tile-ns  new 99%tile-ns  delta
ReadMemStatsLatency-8       147M ±18%         4M ±57%  -97.43%  (p=0.008 n=5+5)

Fixes #19812.

Change-Id: If66c3c97d171524ae29f0e7af4bd33509d9fd0bb
Reviewed-on: https://go-review.googlesource.com/c/go/+/216557
Run-TryBot: Michael Knyszek 
TryBot-Result: Gobot Gobot 
Reviewed-by: Cherry Zhang

Revert "runtime: don't hold worldsema across mark phase"

2020-01-24T23:27:33+00:00

This reverts commit 7b294cdd8df0a9523010f6ffc80c59e64578f34b, CL 182657.

Reason for revert: This change may be causing latency problems
for applications which call ReadMemStats, because it may cause
all goroutines to stop until the GC completes.

https://golang.org/cl/215157 fixes this problem, but it's too
late in the cycle to land that.

Updates #19812.

Change-Id: Iaa26f4dec9b06b9db2a771a44e45f58d0aa8f26d
Reviewed-on: https://go-review.googlesource.com/c/go/+/216358
Run-TryBot: Michael Knyszek 
TryBot-Result: Gobot Gobot 
Reviewed-by: Cherry Zhang

runtime: don't hold worldsema across mark phase

2019-09-04T15:53:59+00:00

This change makes it so that worldsema isn't held across the mark phase.
This means that various operations like ReadMemStats may now stop the
world during the mark phase, reducing latency on such operations.

Only three such operations are still no longer allowed to occur during
marking: GOMAXPROCS, StartTrace, and StopTrace.

For the former it's because any change to GOMAXPROCS impacts GC mark
background worker scheduling and the details there are tricky.

For the latter two it's because tracing needs to observe consistent GC
start and GC end events, and if StartTrace or StopTrace may stop the
world during marking, then it's possible for it to see a GC end event
without a start or GC start event without an end, respectively.

To ensure that GOMAXPROCS and StartTrace/StopTrace cannot proceed until
marking is complete, the runtime now holds a new semaphore, gcsema,
across the mark phase just like it used to with worldsema.

Fixes #19812.

Change-Id: I15d43ed184f711b3d104e8f267fb86e335f86bf9
Reviewed-on: https://go-review.googlesource.com/c/go/+/182657
Run-TryBot: Michael Knyszek 
TryBot-Result: Gobot Gobot 
Reviewed-by: Keith Randall 
Reviewed-by: Cherry Zhang

cmd/go: move runtime/debug.modinfo to runtime.modinfo

2019-04-23T14:21:30+00:00

It is easier to ensure that the symbol is always present
if we move it to package runtime. Avoids init-time work.
Also moves it next to buildVersion, the other similar symbol.

Setting up for "go version ".

For #31624.

Change-Id: I943724469ce6992153e701257eb6f12da88c8e4e
Reviewed-on: https://go-review.googlesource.com/c/go/+/173341
Run-TryBot: Russ Cox 
TryBot-Result: Gobot Gobot 
Reviewed-by: Brad Fitzpatrick

runtime: add js/wasm architecture

2018-05-08T00:17:34+00:00

This commit adds the js/wasm architecture to the runtime package.
Currently WebAssembly has no support for threads yet, see
https://github.com/WebAssembly/design/issues/1073. Because of that,
there is no preemption of goroutines and no sysmon goroutine.

Design doc: https://docs.google.com/document/d/131vjr4DH6JFnb-blm_uRdaC0_Nv3OUwjEY5qVCxCup4
About WebAssembly assembly files: https://docs.google.com/document/d/1GRmy3rA4DiYtBlX-I1Jr_iHykbX8EixC3Mq0TCYqbKc

Updates #18892

Change-Id: I7f12d21b5180500d55ae9fd2f7e926a1731db391
Reviewed-on: https://go-review.googlesource.com/103877
Run-TryBot: Brad Fitzpatrick 
TryBot-Result: Gobot Gobot 
Reviewed-by: Austin Clements

runtime: eliminate GOMAXPROCS limit

2017-09-27T16:29:12+00:00

Now that allp is dynamically allocated, there's no need for a hard cap
on GOMAXPROCS.

Fixes #15131.

Change-Id: I53eee8e228a711a818f7ebce8d9fd915b3865eed
Reviewed-on: https://go-review.googlesource.com/45574
Run-TryBot: Austin Clements 
TryBot-Result: Gobot Gobot 
Reviewed-by: Rick Hudson 
Reviewed-by: Brad Fitzpatrick

all: single space after period.

2016-03-02T00:13:47+00:00

The tree's pretty inconsistent about single space vs double space
after a period in documentation. Make it consistently a single space,
per earlier decisions. This means contributors won't be confused by
misleading precedence.

This CL doesn't use go/doc to parse. It only addresses // comments.
It was generated with:

$ perl -i -npe 's,^(\s*// .+[a-z]\.)  +([A-Z]),$1 $2,' $(git grep -l -E '^\s*//(.+\.)  +([A-Z])')
$ go test go/doc -update

Change-Id: Iccdb99c37c797ef1f804a94b22ba5ee4b500c4f7
Reviewed-on: https://go-review.googlesource.com/20022
Reviewed-by: Rob Pike 
Reviewed-by: Dave Day 
Run-TryBot: Brad Fitzpatrick 
TryBot-Result: Gobot Gobot

runtime: document that NumCPU does not change

2015-12-05T20:16:35+00:00

Fixes #11609.

Change-Id: I3cf64164fde28ebf739706728b84d8ef5b6dc90e
Reviewed-on: https://go-review.googlesource.com/17456
Reviewed-by: Ian Lance Taylor

runtime: break atomics out into package runtime/internal/atomic

2015-11-10T17:38:04+00:00

This change breaks out most of the atomics functions in the runtime
into package runtime/internal/atomic. It adds some basic support
in the toolchain for runtime packages, and also modifies linux/arm
atomics to remove the dependency on the runtime's mutex. The mutexes
have been replaced with spinlocks.

all trybots are happy!
In addition to the trybots, I've tested on the darwin/arm64 builder,
on the darwin/arm builder, and on a ppc64le machine.

Change-Id: I6698c8e3cf3834f55ce5824059f44d00dc8e3c2f
Reviewed-on: https://go-review.googlesource.com/14204
Run-TryBot: Michael Matloob 
Reviewed-by: Russ Cox