b75b4d0ee6
If there are no netpoll waiters then calling netpoll will never find any goroutines. The later blocking netpoll in findrunnable already has this optimization. With golang.org/cl/78538 also applied, this change has a small impact on latency: name old time/op new time/op delta WakeupParallelSpinning/0s-12 13.6µs ± 1% 13.7µs ± 1% ~ (p=0.873 n=19+20) WakeupParallelSpinning/1µs-12 17.7µs ± 0% 17.6µs ± 0% -0.31% (p=0.000 n=20+20) WakeupParallelSpinning/2µs-12 20.2µs ± 2% 19.9µs ± 1% -1.59% (p=0.000 n=20+19) WakeupParallelSpinning/5µs-12 32.0µs ± 1% 32.1µs ± 1% ~ (p=0.201 n=20+19) WakeupParallelSpinning/10µs-12 51.7µs ± 0% 51.4µs ± 1% -0.60% (p=0.000 n=20+18) WakeupParallelSpinning/20µs-12 92.2µs ± 0% 92.2µs ± 0% ~ (p=0.474 n=19+19) WakeupParallelSpinning/50µs-12 215µs ± 0% 215µs ± 0% ~ (p=0.319 n=20+19) WakeupParallelSpinning/100µs-12 330µs ± 2% 331µs ± 2% ~ (p=0.296 n=20+19) WakeupParallelSyscall/0s-12 127µs ± 0% 126µs ± 0% -0.57% (p=0.000 n=18+18) WakeupParallelSyscall/1µs-12 129µs ± 0% 128µs ± 1% -0.43% (p=0.000 n=18+19) WakeupParallelSyscall/2µs-12 131µs ± 1% 130µs ± 1% -0.78% (p=0.000 n=20+19) WakeupParallelSyscall/5µs-12 137µs ± 1% 136µs ± 0% -0.54% (p=0.000 n=18+19) WakeupParallelSyscall/10µs-12 147µs ± 1% 146µs ± 0% -0.58% (p=0.000 n=18+19) WakeupParallelSyscall/20µs-12 168µs ± 0% 167µs ± 0% -0.52% (p=0.000 n=19+19) WakeupParallelSyscall/50µs-12 228µs ± 0% 227µs ± 0% -0.37% (p=0.000 n=19+18) WakeupParallelSyscall/100µs-12 329µs ± 0% 328µs ± 0% -0.28% (p=0.000 n=20+18) There is a bigger improvement in CPU utilization. Before this CL, these benchmarks spent 12% of cycles in netpoll, which are gone after this CL. This also fixes the sched.lastpoll load, which should be atomic. Change-Id: I600961460608bd5ba3eeddc599493d2be62064c6 Reviewed-on: https://go-review.googlesource.com/78915 Run-TryBot: Michael Pratt <mpratt@google.com> TryBot-Result: Gobot Gobot <gobot@golang.org> Reviewed-by: Dmitry Vyukov <dvyukov@google.com> Reviewed-by: Austin Clements <austin@google.com> |
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