runtime: align vgetrandom states to cache line

This prevents false sharing, which makes a large difference on machines
with several NUMA nodes, such as this dual socket server:

cpu: Intel(R) Xeon(R) Gold 6338 CPU @ 2.00GHz
                      │    sec/op    │    sec/op     vs base                │
ParallelGetRandom-128   0.7944n ± 5%   0.4503n ± 0%  -43.31% (p=0.000 n=10)

                      │     B/s      │     B/s       vs base                │
ParallelGetRandom-128   4.690Gi ± 5%   8.272Gi ± 0%  +76.38% (p=0.000 n=10)

Change-Id: Id4421e9a4c190b38aff0be4c59e9067b0a38ccd7
Reviewed-on: https://go-review.googlesource.com/c/go/+/616535
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Jason Donenfeld <Jason@zx2c4.com>
Reviewed-by: David Chase <drchase@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>

1 files changed, 22 insertions, 0 deletions

diff --git a/src/internal/syscall/unix/getrandom_linux_test.go b/src/internal/syscall/unix/getrandom_linux_test.go
new file mode 100644
index 0000000000..e1778c19e8
--- /dev/null
+++ b/src/internal/syscall/unix/getrandom_linux_test.go
@@ -0,0 +1,22 @@
+// Copyright 2024 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package unix_test
+
+import (
+	"internal/syscall/unix"
+	"testing"
+)
+
+func BenchmarkParallelGetRandom(b *testing.B) {
+	b.SetBytes(4)
+	b.RunParallel(func(pb *testing.PB) {
+		var buf [4]byte
+		for pb.Next() {
+			if _, err := unix.GetRandom(buf[:], 0); err != nil {
+				b.Fatal(err)
+			}
+		}
+	})
+}