From 0cc1290174751971d282196e21ec9037b217e5a5 Mon Sep 17 00:00:00 2001 From: Andy Pan Date: Fri, 27 Mar 2020 03:21:17 +0000 Subject: runtime: converge duplicate calls to netpollBreak into one MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit There might be some concurrent (maybe not concurrent, just sequential but in a short time window) and duplicate calls to `netpollBreak`, trying to wake up a net-poller. If one has called `netpollBreak` and that waking event hasn't been received by epollwait/kevent/..., then the subsequent calls of `netpollBreak` ought to be ignored or in other words, these calls should be converged into one. Benchmarks go1.13.5 darwin/amd64: benchmark-func time/op (old) time/op (new) delta BenchmarkNetpollBreak-4 29668ns ±1% 3131ns ±2% -89.45% mem/B (old) mem/B (new) delta 154B ±13% 0B ±0% -100% Change-Id: I3cf757a5d6edc5a99adad7aea3baee4b7f2a8f5c GitHub-Last-Rev: 15bcfbab8a5db51f65da01315a5880a5dbf9e028 GitHub-Pull-Request: golang/go#36294 Reviewed-on: https://go-review.googlesource.com/c/go/+/212737 Run-TryBot: Emmanuel Odeke TryBot-Result: Gobot Gobot Reviewed-by: Ian Lance Taylor --- src/runtime/netpoll_kqueue.go | 30 +++++++++++++++++++----------- 1 file changed, 19 insertions(+), 11 deletions(-) (limited to 'src/runtime/netpoll_kqueue.go') diff --git a/src/runtime/netpoll_kqueue.go b/src/runtime/netpoll_kqueue.go index 39d402252d..2ff21d8fcb 100644 --- a/src/runtime/netpoll_kqueue.go +++ b/src/runtime/netpoll_kqueue.go @@ -8,12 +8,17 @@ package runtime // Integrated network poller (kqueue-based implementation). -import "unsafe" +import ( + "runtime/internal/atomic" + "unsafe" +) var ( kq int32 = -1 netpollBreakRd, netpollBreakWr uintptr // for netpollBreak + + netpollWakeSig uintptr // used to avoid duplicate calls of netpollBreak ) func netpollinit() { @@ -78,17 +83,19 @@ func netpollarm(pd *pollDesc, mode int) { // netpollBreak interrupts a kevent. func netpollBreak() { - for { - var b byte - n := write(netpollBreakWr, unsafe.Pointer(&b), 1) - if n == 1 || n == -_EAGAIN { - break - } - if n == -_EINTR { - continue + if atomic.Casuintptr(&netpollWakeSig, 0, 1) { + for { + var b byte + n := write(netpollBreakWr, unsafe.Pointer(&b), 1) + if n == 1 || n == -_EAGAIN { + break + } + if n == -_EINTR { + continue + } + println("runtime: netpollBreak write failed with", -n) + throw("runtime: netpollBreak write failed") } - println("runtime: netpollBreak write failed with", -n) - throw("runtime: netpollBreak write failed") } } @@ -145,6 +152,7 @@ retry: // if blocking. var tmp [16]byte read(int32(netpollBreakRd), noescape(unsafe.Pointer(&tmp[0])), int32(len(tmp))) + atomic.Storeuintptr(&netpollWakeSig, 0) } continue } -- cgit v1.3-5-g9baa