From 352dd2d932c1c1c6dbc3e112fcdfface07d4fffb Mon Sep 17 00:00:00 2001
From: Ian Lance Taylor <iant@golang.org>
Date: Wed, 14 Feb 2024 17:54:00 -0800
Subject: [PATCH] runtime: only poll network from one P at a time in
findRunnable
For #65064
Change-Id: Ifecd7e332d2cf251750752743befeda4ed396f33
Reviewed-on: https://go-review.googlesource.com/c/go/+/564197
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Artur M. Wolff <artur.m.wolff@gmail.com>
Reviewed-by: Carlos Amedee <carlos@golang.org>
Reviewed-by: Mauri de Souza Meneguzzo <mauri870@gmail.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
---
src/runtime/proc.go | 8 ++++++--
src/runtime/runtime2.go | 7 ++++---
2 files changed, 10 insertions(+), 5 deletions(-)
diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index db7a5b2bb1c..44c6d0b4e43 100644
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -3387,8 +3387,12 @@ top:
// blocked thread (e.g. it has already returned from netpoll, but does
// not set lastpoll yet), this thread will do blocking netpoll below
// anyway.
- if netpollinited() && netpollAnyWaiters() && sched.lastpoll.Load() != 0 {
- if list, delta := netpoll(0); !list.empty() { // non-blocking
+ // We only poll from one thread at a time to avoid kernel contention
+ // on machines with many cores.
+ if netpollinited() && netpollAnyWaiters() && sched.lastpoll.Load() != 0 && sched.pollingNet.Swap(1) == 0 {
+ list, delta := netpoll(0)
+ sched.pollingNet.Store(0)
+ if !list.empty() { // non-blocking
gp := list.pop()
injectglist(&list)
netpollAdjustWaiters(delta)
diff --git a/src/runtime/runtime2.go b/src/runtime/runtime2.go
index e56b45053e1..27d14b890bd 100644
--- a/src/runtime/runtime2.go
+++ b/src/runtime/runtime2.go
@@ -757,9 +757,10 @@ type p struct {
}
type schedt struct {
- goidgen atomic.Uint64
- lastpoll atomic.Int64 // time of last network poll, 0 if currently polling
- pollUntil atomic.Int64 // time to which current poll is sleeping
+ goidgen atomic.Uint64
+ lastpoll atomic.Int64 // time of last network poll, 0 if currently polling
+ pollUntil atomic.Int64 // time to which current poll is sleeping
+ pollingNet atomic.Int32 // 1 if some P doing non-blocking network poll
lock mutex
--
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