runtime.SetMutexProfileFraction(n int) will capture 1/n-th of stack
traces of goroutines holding contended mutexes if n > 0. From runtime/pprof,
pprot.Lookup("mutex").WriteTo writes the accumulated
stack traces to w (in essentially the same format that blocking
profiling uses).
Change-Id: Ie0b54fa4226853d99aa42c14cb529ae586a8335a
Reviewed-on: https://go-review.googlesource.com/29650
Reviewed-by: Austin Clements <austin@google.com>
The panic leaves the lock in an unusable state. Trying to panic with a usable state makes the lock significantly less efficient and scalable (see early CL patch sets and discussion). Instead, use runtime.throw, which will crash the program directly. In general throw is reserved for when the runtime detects truly serious, unrecoverable problems. This problem is certainly serious, and, without a significant performance hit, is unrecoverable. Fixes #13879. Change-Id: I41920d9e2317270c6f909957d195bd8b68177f8d Reviewed-on: https://go-review.googlesource.com/31359 Reviewed-by: Austin Clements <austin@google.com> Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
Embed noLock struct into the following types, so `go vet -copylocks` catches their copying additionally to types containing sync.Mutex: - sync.Cond - sync.WaitGroup - sync.Pool - atomic.Value Fixes #14582 Change-Id: Icb543ef5ad10524ad239a15eec8a9b334b0e0660 Reviewed-on: https://go-review.googlesource.com/22015 Reviewed-by: Russ Cox <rsc@golang.org> Run-TryBot: Russ Cox <rsc@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org>
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 <r@golang.org> Reviewed-by: Dave Day <djd@golang.org> Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org> TryBot-Result: Gobot Gobot <gobot@golang.org>
Factor out duplicated race thunks from sync, syscall net and fmt packages into a separate package and use it. Fixes #8593 Change-Id: I156869c50946277809f6b509463752e7f7d28cdb Reviewed-on: https://go-review.googlesource.com/14870 Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org> Run-TryBot: Dmitry Vyukov <dvyukov@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org>
Currently sync.Mutex is fully cooperative. That is, once contention is discovered, the goroutine calls into scheduler. This is suboptimal as the resource can become free soon after (especially if critical sections are short). Server software usually runs at ~~50% CPU utilization, that is, switching to other goroutines is not necessary profitable. This change adds limited active spinning to sync.Mutex if: 1. running on a multicore machine and 2. GOMAXPROCS>1 and 3. there is at least one other running P and 4. local runq is empty. As opposed to runtime mutex we don't do passive spinning, because there can be work on global runq on on other Ps. benchmark old ns/op new ns/op delta BenchmarkMutexNoSpin 1271 1272 +0.08% BenchmarkMutexNoSpin-2 702 683 -2.71% BenchmarkMutexNoSpin-4 377 372 -1.33% BenchmarkMutexNoSpin-8 197 190 -3.55% BenchmarkMutexNoSpin-16 131 122 -6.87% BenchmarkMutexNoSpin-32 170 164 -3.53% BenchmarkMutexSpin 4724 4728 +0.08% BenchmarkMutexSpin-2 2501 2491 -0.40% BenchmarkMutexSpin-4 1330 1325 -0.38% BenchmarkMutexSpin-8 684 684 +0.00% BenchmarkMutexSpin-16 414 372 -10.14% BenchmarkMutexSpin-32 559 469 -16.10% BenchmarkMutex 19.1 19.1 +0.00% BenchmarkMutex-2 81.6 54.3 -33.46% BenchmarkMutex-4 143 100 -30.07% BenchmarkMutex-8 154 156 +1.30% BenchmarkMutex-16 140 159 +13.57% BenchmarkMutex-32 141 163 +15.60% BenchmarkMutexSlack 33.3 31.2 -6.31% BenchmarkMutexSlack-2 122 97.7 -19.92% BenchmarkMutexSlack-4 168 158 -5.95% BenchmarkMutexSlack-8 152 158 +3.95% BenchmarkMutexSlack-16 140 159 +13.57% BenchmarkMutexSlack-32 146 162 +10.96% BenchmarkMutexWork 154 154 +0.00% BenchmarkMutexWork-2 89.2 89.9 +0.78% BenchmarkMutexWork-4 139 86.1 -38.06% BenchmarkMutexWork-8 177 162 -8.47% BenchmarkMutexWork-16 170 173 +1.76% BenchmarkMutexWork-32 176 176 +0.00% BenchmarkMutexWorkSlack 160 160 +0.00% BenchmarkMutexWorkSlack-2 103 99.1 -3.79% BenchmarkMutexWorkSlack-4 155 148 -4.52% BenchmarkMutexWorkSlack-8 176 170 -3.41% BenchmarkMutexWorkSlack-16 170 173 +1.76% BenchmarkMutexWorkSlack-32 175 176 +0.57% "No work" benchmarks are not very interesting (BenchmarkMutex and BenchmarkMutexSlack), as they are absolutely not realistic. Fixes #8889 Change-Id: I6f14f42af1fa48f73a776fdd11f0af6dd2bb428b Reviewed-on: https://go-review.googlesource.com/5430 Reviewed-by: Rick Hudson <rlh@golang.org> Run-TryBot: Dmitry Vyukov <dvyukov@google.com>
Preparation was in CL 134570043. This CL contains only the effect of 'hg mv src/pkg/* src'. For more about the move, see golang.org/s/go14nopkg.