build: all.bash fails to saturate 6 cores #17751

bcmills · 2016-11-02T21:42:11Z

go version devel +eed2bb7 Wed Nov 2 19:21:16 2016 +0000 linux/amd64

What did you do?

./clean.bash
time ./all.bash

What did you expect to see?

I do my development on a virtualized 6-core Xeon running Ubuntu. (runtime.NumCPU() returns 6.)

Per @rsc's comments on #10571, I expected "Both the build half and the test half of all.bash should consume nearly all the CPUs for most of the time."

What did you see instead?

all.bash seems to saturate at ~2 CPU cores for a significant fraction of the run. It consumes less than twice as much user time than real. Oddly, sys usage is even higher than user; I'm not sure what to make of that.

real    8m55.199s
user    14m13.511s
sys     8m51.402s

Here's a chart of CPU saturation over time as measured by mpstat. You can see that there are a couple bursts of parallelism with mostly poor saturation in between. The machine doesn't appear to be hitting swap during the build.

The text was updated successfully, but these errors were encountered:

bradfitz · 2016-11-02T21:49:28Z

I don't have access to your CPU saturation chart. google.com accounts can't share outside of Google, IIRC. Use your golang account?

bcmills · 2016-11-02T21:56:57Z

That's annoying. I don't have a golang account; I'll see if I can just upload an image instead.

bcmills · 2016-11-02T21:57:18Z

minux · 2016-11-02T22:58:08Z

The low cpu utilization might be caused by non-optimal cmd/go scheduling. I'm more worried about the high sys time, because it usually indicates extensive unbuffered IO. However, I couldn't reproduce the high %sys usage on my Linux system, and /usr/bin/time reports that average CPU usage to be 353% on a 4 core HT system (8 logical cores).

bradfitz · 2016-11-02T23:13:05Z

on a virtualized 6-core Xeon

Which virtualization? (might explain high sys time?)

josharian · 2016-11-03T00:26:22Z

#15736 will help with understanding this. Sorry I didn't get it into 1.8. Making compilation more concurrent will also help saturate the cores (as would #15734, but the consensus is to focus on intra-package concurrency instead).

bradfitz · 2016-11-03T00:29:09Z

Also, the make.bash portion of Bryan's graph doesn't look super terrible.

The terrible part is running the tests, almost none of which use t.Parallel so are run serialized.

If people could go around and sprinkle some magic t.Parallel fairy dusty on tests where it's safe to do (where it doesn't introduce flakiness under load), that would be great.

josharian · 2016-11-03T00:46:36Z

Here are the 20 slowest packages to test, at least on my machine:

$ pbpaste | grep "^ok" | awk '{print $3"\t"$2}' | sort -n -r | head -n 20
67.474s cmd/go
54.461s runtime
42.232s cmd/compile/internal/gc
10.048s net/http
9.891s  go/build
9.311s  cmd/objdump
8.648s  cmd/cover
8.295s  cmd/vet
7.839s  net
6.487s  cmd/nm
5.483s  cmd/pack
4.813s  cmd/compile
4.534s  os/signal
3.899s  cmd/addr2line
2.784s  net/http/cgi
2.692s  time
2.615s  go/types
2.246s  log/syslog
2.209s  compress/flate
2.176s  runtime/pprof

Of these, cmd/go, runtime, net/http, net, os/signal, net/http/cgi, time, and runtime/pprof seem the most likely to become flakier under load. I'll take a look at cmd/compile/internal/gc and leave the rest for others.

dsnet · 2016-11-03T00:48:48Z

I can hammer on compress/flate. It's a package whose tests I want to clean up anyways.

bradfitz · 2016-11-03T00:51:42Z

Here are the 20 slowest packages to test, at least on my machine

I have the timing data for every trybot + build run on all machines in BigQuery, btw.

gopherbot · 2016-11-03T01:00:07Z

CL https://golang.org/cl/32585 mentions this issue.

TestAssembly takes 20s on my machine, which is too slow for normal operation. Marking as -short has its dangers (#17472), but hopefully we'll soon have a builder for that. All the SSA tests are hermetic and not time sensitive and can thus be run in parallel. Reduces the cmd/compile/internal/gc test time during all.bash on my laptop from 42s to 7s. Updates #17751 Change-Id: Idd876421db23b9fa3475e8a9b3355a5dc92a5a29 Reviewed-on: https://go-review.googlesource.com/32585 Run-TryBot: Josh Bleecher Snyder <[email protected]> Reviewed-by: Brad Fitzpatrick <[email protected]>

gopherbot · 2016-11-03T06:00:12Z

CL https://golang.org/cl/32673 mentions this issue.

bcmills · 2016-11-03T17:02:47Z

@bradfitz

Which virtualization? (might explain high sys time?)

Xen (via Ganeti), I believe.

I suspect that I/O performance on my system is pretty poor, so that might explain the high sys time.

Rebuild cmd/objdump once instead of twice. Speeds up standalone 'go test cmd/objdump' on my machine from ~1.4s to ~1s. Updates #17751 Change-Id: I15fd79cf18c310f892bc28a9e9ca47ee010c989a Reviewed-on: https://go-review.googlesource.com/32673 Run-TryBot: Josh Bleecher Snyder <[email protected]> TryBot-Result: Gobot Gobot <[email protected]> Reviewed-by: Brad Fitzpatrick <[email protected]>

gopherbot · 2016-11-04T03:35:17Z

CL https://golang.org/cl/32684 mentions this issue.

Before: 8.9 seconds for go test -short After: 2.8 seconds There are still 250 tests without t.Parallel, but I got the important onces using a script: $ go test -short -v 2>&1 | go run ~/slowtests.go Where slowtests.go is https://play.golang.org/p/9mh5Wg1nLN The remaining 250 (the output lines from slowtests.go) all have a reported duration of 0ms, except one 50ms test which has to be serial. Where tests can't be parallel, I left a comment at the top saying why, so people don't add t.Parallel later and get surprised at failures. Updates #17751 Change-Id: Icbe32cbe2b996e23c89f1af6339287fa22af5115 Reviewed-on: https://go-review.googlesource.com/32684 Run-TryBot: Brad Fitzpatrick <[email protected]> TryBot-Result: Gobot Gobot <[email protected]> Reviewed-by: Josh Bleecher Snyder <[email protected]>

gopherbot · 2016-11-04T06:00:08Z

CL https://golang.org/cl/32751 mentions this issue.

I used the slowtests.go tool as described in https://golang.org/cl/32684 on packages that stood out. go test -short std drops from ~56 to ~52 seconds. This isn't a huge win, but it was mostly an exercise. Updates #17751 Change-Id: I9f3402e36a038d71e662d06ce2c1d52f6c4b674d Reviewed-on: https://go-review.googlesource.com/32751 Run-TryBot: Brad Fitzpatrick <[email protected]> TryBot-Result: Gobot Gobot <[email protected]> Reviewed-by: Ian Lance Taylor <[email protected]>

gopherbot · 2016-11-04T20:00:14Z

CL https://golang.org/cl/32754 mentions this issue.

Was 2.3 seconds. Now 1.4 seconds. Next win would be not running a child process and refactoring main so it could be called from tests easily. But that would also require rewriting the errchk written in Perl. This appears to be the last user of errchk in the tree. Updates #17751 Change-Id: Id7c3cec76f438590789b994e756f55b5397be07f Reviewed-on: https://go-review.googlesource.com/32754 Run-TryBot: Brad Fitzpatrick <[email protected]> TryBot-Result: Gobot Gobot <[email protected]> Reviewed-by: Rob Pike <[email protected]>

gopherbot · 2016-11-07T01:25:07Z

CL https://golang.org/cl/32850 mentions this issue.

Cuts tests from 35 to 25 seconds. Many of these could be parallel if the test runner were modified to give each test its own workdir cloned from the tempdir files they use. But later. This helps for now. Updates #17751 Change-Id: Icc2ff87cca60a33ec5fd8abb1eb0a9ca3e85bf95 Reviewed-on: https://go-review.googlesource.com/32850 Run-TryBot: Brad Fitzpatrick <[email protected]> TryBot-Result: Gobot Gobot <[email protected]> Reviewed-by: Ian Lance Taylor <[email protected]>

josharian · 2017-08-04T16:16:58Z

I'm curious whether concurrent compilation in 1.9 helps much here.

bcmills · 2017-09-13T17:39:25Z

I'm curious whether concurrent compilation in 1.9 helps much here.

The initial build transient seems to saturate a bit better, and a few of the tests spike to saturation, but the overall utilization is still pretty similar.

From a clean build at tip:

Part of converting all tests to script framework to improve test parallelism. Updates #36320 Updates #17751 Change-Id: I1328a87e2481b4555b01df5c898f1a8015412adc Reviewed-on: https://go-review.googlesource.com/c/go/+/214296 Reviewed-by: Jay Conrod <[email protected]>

Part of converting all tests to script framework to improve test parallelism. Updates #36320 Updates #17751 Change-Id: I27e52c4eabfcd1782965f17c098719dd0ea7e3ca Reviewed-on: https://go-review.googlesource.com/c/go/+/214390 Reviewed-by: Jay Conrod <[email protected]>

Part of converting all tests to script framework to improve test parallelism. Updates #36320 Updates #17751 Change-Id: Ib1c55a48fafb5ce040ac70707bbc2a3ee5e2ddd4 Reviewed-on: https://go-review.googlesource.com/c/go/+/214382 Reviewed-by: Bryan C. Mills <[email protected]> Reviewed-by: Jay Conrod <[email protected]>

Part of converting all tests to script framework to improve test parallelism. Updates #36320 Updates #17751 Change-Id: I69c69809fb1698c8198ef3ea00103a9acb7b6ce7 Reviewed-on: https://go-review.googlesource.com/c/go/+/214387 Run-TryBot: Michael Matloob <[email protected]> Reviewed-by: Jay Conrod <[email protected]>

Part of converting all tests to script framework to improve test parallelism. Updates #36320 Updates #17751 Change-Id: I2170f427c238e9fe8c029b43b346621d82c5e8fc Reviewed-on: https://go-review.googlesource.com/c/go/+/214388 Reviewed-by: Jay Conrod <[email protected]>

Part of converting all tests to script framework to improve test parallelism. Updates #36320 Updates #17751 Change-Id: I16fb0910196c96caef6ed380f96010a548407f9e Reviewed-on: https://go-review.googlesource.com/c/go/+/214424 Reviewed-by: Bryan C. Mills <[email protected]>

Part of converting all tests to script framework to improve test parallelism. Updates #36320 Updates #17751 Change-Id: I2d14c07c590cc618c66f27fdc3a2bb8120c6d646 Reviewed-on: https://go-review.googlesource.com/c/go/+/214427 Reviewed-by: Jay Conrod <[email protected]>

Part of converting all tests to script framework to improve test parallelism. Updates #36320 Updates #17751 Change-Id: I1cb3e2e28700b05b08933f4e24cd996268c1f163 Reviewed-on: https://go-review.googlesource.com/c/go/+/214428 Reviewed-by: Jay Conrod <[email protected]>

Part of converting all tests to script framework to improve test parallelism. Updates #36320 Updates #17751 Change-Id: I6db652a4a515daf6e87645d34191dc9a441f5720 Reviewed-on: https://go-review.googlesource.com/c/go/+/214431 Reviewed-by: Bryan C. Mills <[email protected]>

gopherbot · 2020-02-20T00:46:39Z

Change https://golang.org/cl/220178 mentions this issue: cmd/go: roll forward "convert TestShadowingLogic to the script framework"

Part of converting all tests to script framework to improve test parallelism. Updates #36320 Updates #17751 Change-Id: I1020feaa4ddb40ff52c46728bc4973cea4c7b066 Reviewed-on: https://go-review.googlesource.com/c/go/+/214391 Reviewed-by: Jay Conrod <[email protected]>

…t framework The name of the test is too long to fit on the first line. It's TestGoTestBuildsAnXtestContainingOnlyNonRunnableExamples. Part of converting all tests to script framework to improve test parallelism. Updates #36320 Updates #17751 Change-Id: I490748271b10a85cbe1d34f9dbecb86ccf0101a7 Reviewed-on: https://go-review.googlesource.com/c/go/+/214423 Reviewed-by: Jay Conrod <[email protected]>

Part of converting all tests to script framework to improve test parallelism. Updates #36320 Updates #17751 Change-Id: If1e591f28d6399a07b37ed7f4a1419bf7cd915eb Reviewed-on: https://go-review.googlesource.com/c/go/+/214425 Reviewed-by: Jay Conrod <[email protected]>

Part of converting all tests to script framework to improve test parallelism. Updates #36320 Updates #17751 Change-Id: I9a99aa5d37300c83a2f95fb906949cb4c1d5356f Reviewed-on: https://go-review.googlesource.com/c/go/+/214426 Reviewed-by: Jay Conrod <[email protected]>

Part of converting all tests to script framework to improve test parallelism. Updates #36320 Updates #17751 Change-Id: I394844da1ffc0dcde7f5862c41ed8efa7c5ca088 Reviewed-on: https://go-review.googlesource.com/c/go/+/214429 Reviewed-by: Jay Conrod <[email protected]>

It looks like TestGoBuildGOPATHOrderBroken has been fixed so I've converted that too, without the skip. Part of converting all tests to script framework to improve test parallelism. Updates #36320 Updates #17751 Change-Id: I7ee77f22fb888811c175bcdc5eb814c80fbec420 Reviewed-on: https://go-review.googlesource.com/c/go/+/214432 Reviewed-by: Jay Conrod <[email protected]>

Part of converting all tests to script framework to improve test parallelism. Updates #36320 Updates #17751 Change-Id: I601e0fcee32b8c5bf2107b520d1dfbe12a19ad3f Reviewed-on: https://go-review.googlesource.com/c/go/+/213223 Reviewed-by: Jay Conrod <[email protected]>

Part of converting all tests to script framework to improve test parallelism. Updates #36320 Updates #17751 Change-Id: Ib386838081abad8bc6b01c1f0a4656553d0b6ff3 Reviewed-on: https://go-review.googlesource.com/c/go/+/214579 Reviewed-by: Jay Conrod <[email protected]>

I think this test needs to be split up eventually. It's one of the longest tests. Part of converting all tests to script framework to improve test parallelism. Updates #36320 Updates #17751 Change-Id: If2168fac040d78fd0ec3dcbdef2affd2a8f48f6d Reviewed-on: https://go-review.googlesource.com/c/go/+/214158 Reviewed-by: Jay Conrod <[email protected]>

This is a bit complex. There's a driver program to run go with modifications to the GOPATH used to test Windows. Also remove the cd method on testgoData, because this was the last function that used it. Part of converting all tests to script framework to improve test parallelism. Updates #36320 Updates #17751 Change-Id: I3e8e27f37fd3701bd36b6365b128dd73b69181c0 Reviewed-on: https://go-review.googlesource.com/c/go/+/214578 Reviewed-by: Jay Conrod <[email protected]>

…ork" This rolls forward the change golang.org/cl/214431, which was reverted in golang.org/cl/220217. The cl was broken because TestVersionControlErrorMessageIncludesCorrectDirectory, which is going to be removed in golang.org/cl/214429 hadn't been submitted yet. Original change description: Part of converting all tests to script framework to improve test parallelism. Updates #36320 Updates #17751 Change-Id: I87b3f9acb8575fbcbd58d454b5f9bac4923429b3 Reviewed-on: https://go-review.googlesource.com/c/go/+/220178 Run-TryBot: Michael Matloob <[email protected]> TryBot-Result: Gobot Gobot <[email protected]> Reviewed-by: Bryan C. Mills <[email protected]>

gopherbot · 2020-03-17T15:09:37Z

Change https://golang.org/cl/223745 mentions this issue: cmd/go: replace TestCgoDependsOnSyscall with a simpler script test

The existing test attempted to remove '_race' binaries from GOROOT/pkg, which could not only fail if GOROOT is read-only, but also interfere with other tests run in parallel. Updates #30316 Updates #37573 Updates #17751 Change-Id: Id7e2286ab67f8333baf4d52244b7f4476aa93a46 Reviewed-on: https://go-review.googlesource.com/c/go/+/223745 Run-TryBot: Bryan C. Mills <[email protected]> Reviewed-by: Jay Conrod <[email protected]> TryBot-Result: Gobot Gobot <[email protected]>

gopherbot · 2020-06-24T14:42:57Z

Change https://golang.org/cl/239738 mentions this issue: [release-branch.go1.14] cmd/go: convert TestBuildIDContainsArchModeEnv to the script framework

gopherbot · 2020-06-24T18:03:01Z

Change https://golang.org/cl/239777 mentions this issue: [release-branch.go1.13] cmd/go: convert TestBuildIDContainsArchModeEnv to the script framework

…v to the script framework Part of converting all tests to script framework to improve test parallelism. Fixes #39824 Updates #36320 Updates #17751 Change-Id: I69c69809fb1698c8198ef3ea00103a9acb7b6ce7 Reviewed-on: https://go-review.googlesource.com/c/go/+/214387 Run-TryBot: Michael Matloob <[email protected]> Reviewed-by: Jay Conrod <[email protected]> (cherry picked from CL 214387) Reviewed-on: https://go-review.googlesource.com/c/go/+/239738 Run-TryBot: Dmitri Shuralyov <[email protected]> TryBot-Result: Gobot Gobot <[email protected]> Reviewed-by: Dmitri Shuralyov <[email protected]> Reviewed-by: Michael Matloob <[email protected]> Reviewed-by: Carlos Amedee <[email protected]>

…v to the script framework Part of converting all tests to script framework to improve test parallelism. Fixes #39823 Updates #36320 Updates #17751 Change-Id: I69c69809fb1698c8198ef3ea00103a9acb7b6ce7 Reviewed-on: https://go-review.googlesource.com/c/go/+/214387 Run-TryBot: Michael Matloob <[email protected]> Reviewed-by: Jay Conrod <[email protected]> (cherry picked from CL 214387) Reviewed-on: https://go-review.googlesource.com/c/go/+/239777 Run-TryBot: Bryan C. Mills <[email protected]> TryBot-Result: Gobot Gobot <[email protected]> Reviewed-by: Dmitri Shuralyov <[email protected]> Reviewed-by: Michael Matloob <[email protected]> Reviewed-by: Carlos Amedee <[email protected]>

bradfitz added help wanted NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. labels Nov 3, 2016

josharian changed the title ~~all.bash fails to saturate 6 cores~~ build: all.bash fails to saturate 6 cores Nov 3, 2016

rsc added this to the Unplanned milestone Jan 4, 2017

bcmills mentioned this issue Aug 4, 2017

proposal: testing: run tests in parallel by default #21214

Closed

bcmills added the help wanted label Sep 20, 2021

bcmills mentioned this issue Sep 20, 2021

cmd/go,cmd/compile: let cmd/compile choose how much concurrency to use #48497

Open

bcmills mentioned this issue Jan 19, 2024

cmd/dist: GOMAXPROCS=2 runtime -cpu=1,2,4 -quick makes poor use of CPU resources, increasing all.bat latency #65164

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build: all.bash fails to saturate 6 cores #17751

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build: all.bash fails to saturate 6 cores #17751

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bcmills commented Nov 2, 2016 • edited Loading

What did you do?

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What did you see instead?

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