net/http: reuse gzip reader from pool for transport #61353

Sunyue · 2023-07-14T10:11:31Z

Line 2858 in 089e37a

gz.zr, gz.zerr = gzip.NewReader(gz.body)

Is it possible to reuse this gzip reader from a sync.Pool to reduce the memory allocation cause by flate.NewReader

The text was updated successfully, but these errors were encountered:

bcmills · 2023-07-14T14:57:55Z

gzip.Reader does have a Reset method, but we would also need some way to know when the gzip.Reader is safe to reuse.

Hmm. (*http.gzipReader).Read already has some locking in Read. Perhaps we could do something like:

func (gz *gzipReader) Read(p []byte) (n int, err error) {
	gz.body.mu.Lock()
	if gz.body.closed {
		err = errReadOnClosedResBody
	} else if gz.zr == nil {
		if gz.zerr == nil {
			zr := gzipPool.Get().(*gzip.Reader)
			gz.zerr = zr.Reset(gz.body)
			if gz.zerr == nil {
				gz.zr = zr
			} else {
				gzipPool.Put(zr)
			}
		}
		err = gz.zerr
	}
	gz.body.mu.Unlock()

	if err != nil {
		return 0, err
	}
	return gz.zr.Read(p)
}

func (gz *gzipReader) Close() error {
	err := gz.body.Close()

	gz.body.mu.Lock()
	if gz.zr != nil {
		gz.zr.Reset(emptyReader{})  // drop reference to gz.body
		gzipPool.Put(gz.zr)
		gz.zr = nil
	}
	gz.body.mu.Unlock()

	return err
}

var (
	gzipPool = sync.Pool{
		New: func() any { return new(gzip.Reader) },
	}
	_ flate.Reader = emptyReader{}
)

type emptyReader struct{}

func (emptyReader) Read([]byte) (int, error) { return 0, io.EOF }
func (emptyReader) ReadByte() (byte, error) { return 0, io.EOF }

Of course, such a change would also need a supporting benchmark. @Sunyue, want to send it for Go 1.22?

(CC @neild)

neild · 2023-07-14T16:20:28Z

Seems like something we could do; I'm happy to review a CL if someone wants to send me one.

For golang#61353

name old time/op new time/op delta GzipReaderInit-8 9.15µs ± 4% 2.38µs ± 9% -74.04% (p=0.000 n=10+10) name old alloc/op new alloc/op delta GzipReaderInit-8 45.5kB ± 0% 4.3kB ± 0% -90.47% (p=0.000 n=10+10) name old allocs/op new allocs/op delta GzipReaderInit-8 10.0 ± 0% 5.0 ± 0% -50.00% (p=0.000 n=10+10) Allocation saving comes from absent compress/flate.(*dictDecoder).init Fixes golang#61353

gopherbot · 2023-07-16T03:01:53Z

Change https://go.dev/cl/510115 mentions this issue: net/http: pool transport gzip readers

name old time/op new time/op delta GzipReaderInit-8 8.97µs ± 6% 2.61µs ± 7% -70.87% (p=0.000 n=10+9) name old alloc/op new alloc/op delta GzipReaderInit-8 45.5kB ± 0% 4.4kB ± 0% -90.36% (p=0.000 n=10+10) name old allocs/op new allocs/op delta GzipReaderInit-8 10.0 ± 0% 6.0 ± 0% -40.00% (p=0.000 n=10+10) Allocation saving comes from absent compress/flate.(*dictDecoder).init Fixes golang#61353

gopherbot · 2023-07-17T01:10:18Z

Change https://go.dev/cl/510255 mentions this issue: net/http: pool transport gzip readers

name old time/op new time/op delta GzipReaderInit-8 8.97µs ± 6% 2.61µs ± 7% -70.87% (p=0.000 n=10+9) name old alloc/op new alloc/op delta GzipReaderInit-8 45.5kB ± 0% 4.4kB ± 0% -90.36% (p=0.000 n=10+10) name old allocs/op new allocs/op delta GzipReaderInit-8 10.0 ± 0% 6.0 ± 0% -40.00% (p=0.000 n=10+10) Allocation saving comes from absent compress/flate.(*dictDecoder).init Fixes golang#61353

AlexanderYastrebov · 2023-07-17T22:02:14Z

Created #61390

For golang#61353

│ old │ new │ │ sec/op │ sec/op vs base │ GzipReaderInit-8 8.940µ ± 4% 2.532µ ± 8% -71.68% (p=0.000 n=10) │ old │ new │ │ B/op │ B/op vs base │ GzipReaderInit-8 44.438Ki ± 0% 4.297Ki ± 0% -90.33% (p=0.000 n=10) │ old │ new │ │ allocs/op │ allocs/op vs base │ GzipReaderInit-8 10.000 ± 0% 6.000 ± 0% -40.00% (p=0.000 n=10) Allocation saving comes from absent compress/flate.(*dictDecoder).init Updates golang#61353

│ old │ new │ │ sec/op │ sec/op vs base │ GzipReaderInit-8 8.854µ ± 5% 2.578µ ± 16% -70.89% (p=0.000 n=10) │ old │ new │ │ B/op │ B/op vs base │ GzipReaderInit-8 44.438Ki ± 0% 4.282Ki ± 0% -90.36% (p=0.000 n=10) │ old │ new │ │ allocs/op │ allocs/op vs base │ GzipReaderInit-8 10.000 ± 0% 6.000 ± 0% -40.00% (p=0.000 n=10) Allocation saving comes from absent compress/flate.(*dictDecoder).init Updates golang#61353

For golang#61353

│ old │ new │ │ sec/op │ sec/op vs base │ GzipReaderInit-8 8.891µ ± 10% 2.570µ ± 8% -71.10% (p=0.000 n=10) │ old │ new │ │ B/op │ B/op vs base │ GzipReaderInit-8 44.438Ki ± 0% 4.282Ki ± 0% -90.36% (p=0.000 n=10) │ old │ new │ │ allocs/op │ allocs/op vs base │ GzipReaderInit-8 10.000 ± 0% 6.000 ± 0% -40.00% (p=0.000 n=10) Allocation saving comes from absent compress/flate.(*dictDecoder).init Updates golang#61353

│ old │ new │ │ sec/op │ sec/op vs base │ GzipReaderInit-8 8.854µ ± 5% 2.578µ ± 16% -70.89% (p=0.000 n=10) │ old │ new │ │ B/op │ B/op vs base │ GzipReaderInit-8 44.438Ki ± 0% 4.282Ki ± 0% -90.36% (p=0.000 n=10) │ old │ new │ │ allocs/op │ allocs/op vs base │ GzipReaderInit-8 10.000 ± 0% 6.000 ± 0% -40.00% (p=0.000 n=10) Allocation saving comes from absent compress/flate.(*dictDecoder).init Updates golang#61353

For golang#61353

│ old │ new │ │ sec/op │ sec/op vs base │ ClientGzip-8 649.4µ ± 4% 644.4µ ± 12% ~ (p=0.739 n=10) │ old │ new │ │ B/op │ B/op vs base │ ClientGzip-8 49.486Ki ± 0% 9.270Ki ± 2% -81.27% (p=0.000 n=10) │ old │ new │ │ allocs/op │ allocs/op vs base │ ClientGzip-8 51.00 ± 0% 46.00 ± 0% -9.80% (p=0.000 n=10) Allocation saving comes from absent compress/flate.(*dictDecoder).init Updates golang#61353

For golang#61353

│ old │ new │ │ sec/op │ sec/op vs base │ ClientGzip-8 649.4µ ± 4% 644.4µ ± 12% ~ (p=0.739 n=10) │ old │ new │ │ B/op │ B/op vs base │ ClientGzip-8 49.486Ki ± 0% 9.270Ki ± 2% -81.27% (p=0.000 n=10) │ old │ new │ │ allocs/op │ allocs/op vs base │ ClientGzip-8 51.00 ± 0% 46.00 ± 0% -9.80% (p=0.000 n=10) Allocation saving comes from absent compress/flate.(*dictDecoder).init Updates golang#61353

goos: linux goarch: amd64 pkg: net/http │ /tmp/BenchmarkClientGzip.old │ /tmp/BenchmarkClientGzip.new │ │ sec/op │ sec/op vs base │ ClientGzip-8 509.6µ ± 7% 545.5µ ± 10% ~ (p=0.218 n=10) │ /tmp/BenchmarkClientGzip.old │ /tmp/BenchmarkClientGzip.new │ │ B/op │ B/op vs base │ ClientGzip-8 48.943Ki ± 0% 8.757Ki ± 1% -82.11% (p=0.000 n=10) │ /tmp/BenchmarkClientGzip.old │ /tmp/BenchmarkClientGzip.new │ │ allocs/op │ allocs/op vs base │ ClientGzip-8 51.00 ± 0% 46.00 ± 0% -9.80% (p=0.000 n=10) Allocation saving comes from absent compress/flate.(*dictDecoder).init Updates golang#61353

For golang#61353

goos: linux goarch: amd64 pkg: net/http │ /tmp/BenchmarkClientGzip.old │ /tmp/BenchmarkClientGzip.new │ │ sec/op │ sec/op vs base │ ClientGzip-8 509.6µ ± 7% 545.5µ ± 10% ~ (p=0.218 n=10) │ /tmp/BenchmarkClientGzip.old │ /tmp/BenchmarkClientGzip.new │ │ B/op │ B/op vs base │ ClientGzip-8 48.943Ki ± 0% 8.757Ki ± 1% -82.11% (p=0.000 n=10) │ /tmp/BenchmarkClientGzip.old │ /tmp/BenchmarkClientGzip.new │ │ allocs/op │ allocs/op vs base │ ClientGzip-8 51.00 ± 0% 46.00 ± 0% -9.80% (p=0.000 n=10) Allocation saving comes from absent compress/flate.(*dictDecoder).init Updates golang#61353

Sunyue changed the title ~~Reuse gzip reader from pool~~ net/http/transport.go: Is it possible to reuse gzip reader from pool Jul 14, 2023

bcmills added Performance NeedsInvestigation Someone must examine and confirm this is a valid issue and not a duplicate of an existing one. labels Jul 14, 2023

bcmills added this to the Backlog milestone Jul 14, 2023

bcmills added the help wanted label Jul 14, 2023

AlexanderYastrebov mentioned this issue Jul 16, 2023

net/http: pool transport gzip readers #61377

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net/http: add transport gzip reader benchmark

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AlexanderYastrebov mentioned this issue Jul 17, 2023

net/http: pool transport gzip readers #61390

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net/http: add transport gzip reader benchmark

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seankhliao changed the title ~~net/http/transport.go: Is it possible to reuse gzip reader from pool~~ net/http: reuse gzip reader from pool for transport Jul 19, 2023

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net/http: add client benchmark for gzip response

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net/http: reuse gzip reader from pool for transport #61353

net/http: reuse gzip reader from pool for transport #61353

Sunyue commented Jul 14, 2023

bcmills commented Jul 14, 2023

neild commented Jul 14, 2023

gopherbot commented Jul 16, 2023

gopherbot commented Jul 17, 2023

AlexanderYastrebov commented Jul 17, 2023

net/http: reuse gzip reader from pool for transport #61353

net/http: reuse gzip reader from pool for transport #61353

Comments

Sunyue commented Jul 14, 2023

bcmills commented Jul 14, 2023

neild commented Jul 14, 2023

gopherbot commented Jul 16, 2023

gopherbot commented Jul 17, 2023

AlexanderYastrebov commented Jul 17, 2023