From 65594d30ad1b1a2ca676c7ea78f4815f83dc4d06 Mon Sep 17 00:00:00 2001 From: Dean Deng Date: Fri, 22 Jan 2021 11:25:13 -0800 Subject: Avoid atomic operations in kcov processing. Atomic operations here significantly slow down gVisor builds with kcov/coverage enabled. Also mark these functions go:norace to avoid complaints from the race detector. PiperOrigin-RevId: 353281865 --- pkg/coverage/coverage.go | 18 ++++++++++++++---- 1 file changed, 14 insertions(+), 4 deletions(-) (limited to 'pkg/coverage') diff --git a/pkg/coverage/coverage.go b/pkg/coverage/coverage.go index fdfe31417..6f3d72e83 100644 --- a/pkg/coverage/coverage.go +++ b/pkg/coverage/coverage.go @@ -26,7 +26,6 @@ import ( "fmt" "io" "sort" - "sync/atomic" "testing" "gvisor.dev/gvisor/pkg/sync" @@ -69,12 +68,18 @@ var globalData struct { } // ClearCoverageData clears existing coverage data. +// +//go:norace func ClearCoverageData() { coverageMu.Lock() defer coverageMu.Unlock() + + // We do not use atomic operations while reading/writing to the counters, + // which would drastically degrade performance. Slight discrepancies due to + // racing is okay for the purposes of kcov. for _, counters := range coverdata.Cover.Counters { for index := 0; index < len(counters); index++ { - atomic.StoreUint32(&counters[index], 0) + counters[index] = 0 } } } @@ -114,6 +119,8 @@ var coveragePool = sync.Pool{ // ensure that each event is only reported once. Due to the limitations of Go // coverage tools, we reset the global coverage data every time this function is // run. +// +//go:norace func ConsumeCoverageData(w io.Writer) int { InitCoverageData() @@ -125,11 +132,14 @@ func ConsumeCoverageData(w io.Writer) int { for fileNum, file := range globalData.files { counters := coverdata.Cover.Counters[file] for index := 0; index < len(counters); index++ { - if atomic.LoadUint32(&counters[index]) == 0 { + // We do not use atomic operations while reading/writing to the counters, + // which would drastically degrade performance. Slight discrepancies due to + // racing is okay for the purposes of kcov. + if counters[index] == 0 { continue } // Non-zero coverage data found; consume it and report as a PC. - atomic.StoreUint32(&counters[index], 0) + counters[index] = 0 pc := globalData.syntheticPCs[fileNum][index] usermem.ByteOrder.PutUint64(pcBuffer[:], pc) n, err := w.Write(pcBuffer[:]) -- cgit v1.2.3