delta/go-git.git/src/runtime/trace, branch dev.cmdgo

all: update to use os.ReadFile, os.WriteFile, os.CreateTemp, os.MkdirTemp

2020-12-09T19:12:23+00:00

As part of #42026, these helpers from io/ioutil were moved to os.
(ioutil.TempFile and TempDir became os.CreateTemp and MkdirTemp.)

Update the Go tree to use the preferred names.

As usual, code compiled with the Go 1.4 bootstrap toolchain
and code vendored from other sources is excluded.

ReadDir changes are in a separate CL, because they are not a
simple search and replace.

For #42026.

Change-Id: If318df0216d57e95ea0c4093b89f65e5b0ababb3
Reviewed-on: https://go-review.googlesource.com/c/go/+/266365
Trust: Russ Cox 
Run-TryBot: Russ Cox 
TryBot-Result: Go Bot 
Reviewed-by: Ian Lance Taylor

runtime: add file copyright header declaration

2020-09-02T10:09:21+00:00

Some files have no copyright notice.
The copyright time is the earliest modification record of the file.

Change-Id: I5698bae16b6b73543e074415877a03348f792951
Reviewed-on: https://go-review.googlesource.com/c/go/+/246378
Run-TryBot: Emmanuel Odeke 
TryBot-Result: Gobot Gobot 
Reviewed-by: Emmanuel Odeke

os, internal/poll: loop on EINTR for all file syscalls

2020-08-19T21:49:56+00:00

When using a FUSE file system, any system call that touches the file
system can return EINTR.

Fixes #40846

Change-Id: I25d32da22cec08dea81ab297291a85ad72db2df7
Reviewed-on: https://go-review.googlesource.com/c/go/+/249178
Run-TryBot: Ian Lance Taylor 
TryBot-Result: Gobot Gobot 
Reviewed-by: Bryan C. Mills

runtime/trace: fix file name in example

2020-06-19T16:14:19+00:00

The preceding paragraph suggests the test run will produce a file called trace.out.
The same name, trace.out, is used in the output from go help testflag, thus we change the go test line instead of changing the preceding paragraph.

Change-Id: Ib1fa7e49e540853e263a2399b16040ea6f41b703
GitHub-Last-Rev: 3535e62bf8dd02dd9955a28e7fa9cca98de89efd
GitHub-Pull-Request: golang/go#39709
Reviewed-on: https://go-review.googlesource.com/c/go/+/238997
Reviewed-by: Hyang-Ah Hana Kim

internal/poll, os: loop on EINTR

2020-05-11T22:38:32+00:00

Historically we've assumed that we can install all signal handlers
with the SA_RESTART flag set, and let the system restart slow functions
if a signal is received. Therefore, we don't have to worry about EINTR.

This is only partially true, and we've added EINTR checks already for
connect, and open/read on Darwin, and sendfile on Solaris.

Other cases have turned up in #36644, #38033, and #38836.

Also, #20400 points out that when Go code is included in a C program,
the C program may install its own signal handlers without SA_RESTART.
In that case, Go code will see EINTR no matter what it does.

So, go ahead and check for EINTR. We don't check in the syscall package;
people using syscalls directly may want to check for EINTR themselves.
But we do check for EINTR in the higher level APIs in os and net,
and retry the system call if we see it.

This change looks safe, but of course we may be missing some cases
where we need to check for EINTR. As such cases turn up, we can add
tests to runtime/testdata/testprogcgo/eintr.go, and fix the code.
If there are any such cases, their handling after this change will be
no worse than it is today.

For #22838
Fixes #20400
Fixes #36644
Fixes #38033
Fixes #38836

Change-Id: I7e46ca8cafed0429c7a2386cc9edc9d9d47a6896
Reviewed-on: https://go-review.googlesource.com/c/go/+/232862
Run-TryBot: Ian Lance Taylor 
TryBot-Result: Gobot Gobot 
Reviewed-by: Bryan C. Mills

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

all: shorten some tests

2019-05-22T12:54:00+00:00

Shorten some of the longest tests that run during all.bash.
Removes 7r 50u 21s from all.bash.

After this change, all.bash is under 5 minutes again on my laptop.

For #26473.

Change-Id: Ie0460aa935808d65460408feaed210fbaa1d5d79
Reviewed-on: https://go-review.googlesource.com/c/go/+/177559
Run-TryBot: Russ Cox 
TryBot-Result: Gobot Gobot 
Reviewed-by: Ian Lance Taylor

runtime/trace: also treat plan9 as a low memory system

2019-04-18T21:49:02+00:00

Fixes #31554
Updates #12032 (also originally about plan9, but later openbsd/arm)

Change-Id: Ib9f35d27a2304f38bf271c38c0b9153d210d8f95
Reviewed-on: https://go-review.googlesource.com/c/go/+/172837
Run-TryBot: Brad Fitzpatrick 
Reviewed-by: David du Colombier <0intro@gmail.com>
TryBot-Result: Gobot Gobot