From 06751c455d89e09d29affc343ca9e38a02e2f5a2 Mon Sep 17 00:00:00 2001 From: Jake Bailey Date: Mon, 24 Mar 2025 16:01:06 -0700 Subject: [PATCH] syscall: cache Errno.Error() on Windows MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Windows is unlike the other OSs and depends on a syscall for most errors. This can be costly; cache the returned string for later reuse. This helps test caching, since errors are written out as string to the test ID, which are often PathErrors wrapping Errnos. For now, only cache ERROR_FILE_NOT_FOUND and ERROR_PATH_NOT_FOUND. goos: windows goarch: amd64 pkg: syscall cpu: Intel(R) Core(TM) i9-10900K CPU @ 3.70GHz │ old.txt │ new.txt │ │ sec/op │ sec/op vs base │ ErrnoString-20 1788.00n ± 1% 11.08n ± 1% -99.38% (p=0.000 n=10) │ old.txt │ new.txt │ │ B/op │ B/op vs base │ ErrnoString-20 48.00 ± 0% 0.00 ± 0% -100.00% (p=0.000 n=10) │ old.txt │ new.txt │ │ allocs/op │ allocs/op vs base │ ErrnoString-20 1.000 ± 0% 0.000 ± 0% -100.00% (p=0.000 n=10) For #72992 Change-Id: I9a0910fa6538772ffc64ef7670b44059a2c7d18c Reviewed-on: https://go-review.googlesource.com/c/go/+/667495 Reviewed-by: Carlos Amedee LUCI-TryBot-Result: Go LUCI Reviewed-by: Alex Brainman Reviewed-by: Quim Muntal Reviewed-by: Junyang Shao Auto-Submit: Carlos Amedee --- src/syscall/syscall_windows.go | 20 ++++++++++++++++++++ src/syscall/syscall_windows_test.go | 7 +++++++ 2 files changed, 27 insertions(+) diff --git a/src/syscall/syscall_windows.go b/src/syscall/syscall_windows.go index c4782031a4..f7fca07301 100644 --- a/src/syscall/syscall_windows.go +++ b/src/syscall/syscall_windows.go @@ -138,12 +138,32 @@ func FormatMessage(flags uint32, msgsrc uint32, msgid uint32, langid uint32, buf return formatMessage(flags, uintptr(msgsrc), msgid, langid, buf, args) } +var errnoErrorCache sync.Map + func (e Errno) Error() string { // deal with special go errors idx := int(e - APPLICATION_ERROR) if 0 <= idx && idx < len(errors) { return errors[idx] } + + cache := false + switch e { + case ERROR_FILE_NOT_FOUND, ERROR_PATH_NOT_FOUND: + if cached, ok := errnoErrorCache.Load(e); ok { + return cached.(string) + } + cache = true + } + + result := e.error() + if cache { + errnoErrorCache.Store(e, result) + } + return result +} + +func (e Errno) error() string { // ask windows for the remaining errors var flags uint32 = FORMAT_MESSAGE_FROM_SYSTEM | FORMAT_MESSAGE_ARGUMENT_ARRAY | FORMAT_MESSAGE_IGNORE_INSERTS b := make([]uint16, 300) diff --git a/src/syscall/syscall_windows_test.go b/src/syscall/syscall_windows_test.go index 882a279692..5e6ba9dbed 100644 --- a/src/syscall/syscall_windows_test.go +++ b/src/syscall/syscall_windows_test.go @@ -299,3 +299,10 @@ func FuzzUTF16FromString(f *testing.F) { } }) } + +func BenchmarkErrnoString(b *testing.B) { + b.ReportAllocs() + for b.Loop() { + _ = syscall.Errno(2).Error() + } +}