Hi Robert, Thanks for your explanation. But how could I "logged the number of operations done per Go routine", which particular debug settings you referring to? It is reasonable that sync.Mutex rely on runtime scheduler but channels do not. However, it is unclear why a significant performance drop appears. Is it possible to determine when the performance will appear?
Best, Changkun On Monday, August 19, 2019 at 10:27:19 PM UTC+2, Robert Engels wrote: > > I think you'll find the reason that the Mutex uses the Go scheduler. The > chan is controlled by a 'mutex' which eventually defers to the OS futex - > and the OS futex is probably more efficient at scheduling in the face of > large contention - although you would think it should be the other way > around. > > I am guessing that if you logged the number of operations done per Go > routine, you will see that the Mutex version is very fair, and the > chan/futex version is unfair - meaning many are starved. > > -----Original Message----- > From: changkun > Sent: Aug 19, 2019 12:50 PM > To: golang-nuts > Subject: [go-nuts] sync.Mutex encounter large performance drop when > goroutine contention more than 3400 > > I am comparing the performance regarding sync.Mutex and Go channels. Here > is my benchmark: https://play.golang.org/p/zLjVtsSx9gd > > The performance comparison visualization is as follows: > > [image: sync.Mutex performance (1).png] > What are the reasons that > > 1. sync.Mutex encounter a large performance drop when the number of > goroutines goes higher than roughly 3400? > 2. Go channels are pretty stable but slower than sync.Mutex before? > > > > Raw bench data by benchstat (go test -bench=. -count=5): > > MutexWrite/goroutines-2400-8 48.6ns ± 1% > MutexWrite/goroutines-2480-8 49.1ns ± 0% > MutexWrite/goroutines-2560-8 49.7ns ± 1% > MutexWrite/goroutines-2640-8 50.5ns ± 3% > MutexWrite/goroutines-2720-8 50.9ns ± 2% > MutexWrite/goroutines-2800-8 51.8ns ± 3% > MutexWrite/goroutines-2880-8 52.5ns ± 2% > MutexWrite/goroutines-2960-8 54.1ns ± 4% > MutexWrite/goroutines-3040-8 54.5ns ± 2% > MutexWrite/goroutines-3120-8 56.1ns ± 3% > MutexWrite/goroutines-3200-8 63.2ns ± 5% > MutexWrite/goroutines-3280-8 77.5ns ± 6% > MutexWrite/goroutines-3360-8 141ns ± 6% > MutexWrite/goroutines-3440-8 239ns ± 8% > MutexWrite/goroutines-3520-8 248ns ± 3% > MutexWrite/goroutines-3600-8 254ns ± 2% > MutexWrite/goroutines-3680-8 256ns ± 1% > MutexWrite/goroutines-3760-8 261ns ± 2% > MutexWrite/goroutines-3840-8 266ns ± 3% > MutexWrite/goroutines-3920-8 276ns ± 3% > MutexWrite/goroutines-4000-8 278ns ± 3% > MutexWrite/goroutines-4080-8 286ns ± 5% > MutexWrite/goroutines-4160-8 293ns ± 4% > MutexWrite/goroutines-4240-8 295ns ± 2% > MutexWrite/goroutines-4320-8 280ns ± 8% > MutexWrite/goroutines-4400-8 294ns ± 9% > MutexWrite/goroutines-4480-8 285ns ±10% > MutexWrite/goroutines-4560-8 290ns ± 8% > MutexWrite/goroutines-4640-8 271ns ± 3% > MutexWrite/goroutines-4720-8 271ns ± 4% > > ChanWrite/goroutines-2400-8 158ns ± 3% > ChanWrite/goroutines-2480-8 159ns ± 2% > ChanWrite/goroutines-2560-8 161ns ± 2% > ChanWrite/goroutines-2640-8 161ns ± 1% > ChanWrite/goroutines-2720-8 163ns ± 1% > ChanWrite/goroutines-2800-8 166ns ± 3% > ChanWrite/goroutines-2880-8 168ns ± 1% > ChanWrite/goroutines-2960-8 176ns ± 4% > ChanWrite/goroutines-3040-8 176ns ± 2% > ChanWrite/goroutines-3120-8 180ns ± 1% > ChanWrite/goroutines-3200-8 180ns ± 1% > ChanWrite/goroutines-3280-8 181ns ± 2% > ChanWrite/goroutines-3360-8 183ns ± 2% > ChanWrite/goroutines-3440-8 188ns ± 3% > ChanWrite/goroutines-3520-8 190ns ± 2% > ChanWrite/goroutines-3600-8 193ns ± 2% > ChanWrite/goroutines-3680-8 196ns ± 3% > ChanWrite/goroutines-3760-8 199ns ± 2% > ChanWrite/goroutines-3840-8 206ns ± 2% > ChanWrite/goroutines-3920-8 209ns ± 2% > ChanWrite/goroutines-4000-8 206ns ± 2% > ChanWrite/goroutines-4080-8 209ns ± 2% > ChanWrite/goroutines-4160-8 208ns ± 2% > ChanWrite/goroutines-4240-8 209ns ± 3% > ChanWrite/goroutines-4320-8 213ns ± 2% > ChanWrite/goroutines-4400-8 209ns ± 2% > ChanWrite/goroutines-4480-8 211ns ± 1% > ChanWrite/goroutines-4560-8 213ns ± 2% > ChanWrite/goroutines-4640-8 215ns ± 1% > ChanWrite/goroutines-4720-8 218ns ± 3% > > > -- > You received this message because you are subscribed to the Google Groups > "golang-nuts" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to golan...@googlegroups.com <javascript:>. > To view this discussion on the web visit > https://groups.google.com/d/msgid/golang-nuts/3275fb21-dfbd-411d-be42-683386e7ebe2%40googlegroups.com > > <https://groups.google.com/d/msgid/golang-nuts/3275fb21-dfbd-411d-be42-683386e7ebe2%40googlegroups.com?utm_medium=email&utm_source=footer> > . > > > > > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. To unsubscribe from this group and stop receiving emails from it, send an email to golang-nuts+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/golang-nuts/77b8dfc3-53d2-4fbe-9538-cd070d47cd34%40googlegroups.com.
