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zstd: Speed up when WithDecoderLowmem(false) #599

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merged 1 commit into from May 24, 2022
Merged

zstd: Speed up when WithDecoderLowmem(false) #599

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47 changes: 44 additions & 3 deletions zstd/decoder_test.go
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Expand Up @@ -1415,7 +1415,27 @@ func benchmarkDecoderWithFile(path string, b *testing.B) {
}

b.Run("multithreaded-writer", func(b *testing.B) {
dec, err := NewReader(nil)
dec, err := NewReader(nil, WithDecoderLowmem(true))
if err != nil {
b.Fatal(err)
}
b.SetBytes(n)
b.ReportAllocs()
b.ResetTimer()
for i := 0; i < b.N; i++ {
err = dec.Reset(bytes.NewBuffer(data))
if err != nil {
b.Fatal(err)
}
_, err := io.CopyN(ioutil.Discard, dec, n)
if err != nil {
b.Fatal(err)
}
}
})

b.Run("multithreaded-writer-himem", func(b *testing.B) {
dec, err := NewReader(nil, WithDecoderLowmem(false))
if err != nil {
b.Fatal(err)
}
Expand All @@ -1436,7 +1456,7 @@ func benchmarkDecoderWithFile(path string, b *testing.B) {
})

b.Run("singlethreaded-writer", func(b *testing.B) {
dec, err := NewReader(nil, WithDecoderConcurrency(1))
dec, err := NewReader(nil, WithDecoderConcurrency(1), WithDecoderLowmem(true))
if err != nil {
b.Fatal(err)
}
Expand All @@ -1457,7 +1477,28 @@ func benchmarkDecoderWithFile(path string, b *testing.B) {
})

b.Run("singlethreaded-writerto", func(b *testing.B) {
dec, err := NewReader(nil, WithDecoderConcurrency(1))
dec, err := NewReader(nil, WithDecoderConcurrency(1), WithDecoderLowmem(true))
if err != nil {
b.Fatal(err)
}

b.SetBytes(n)
b.ReportAllocs()
b.ResetTimer()
for i := 0; i < b.N; i++ {
err = dec.Reset(bytes.NewBuffer(data))
if err != nil {
b.Fatal(err)
}
// io.Copy will use io.WriterTo
_, err := io.Copy(ioutil.Discard, dec)
if err != nil {
b.Fatal(err)
}
}
})
b.Run("singlethreaded-himem", func(b *testing.B) {
dec, err := NewReader(nil, WithDecoderConcurrency(1), WithDecoderLowmem(false))
if err != nil {
b.Fatal(err)
}
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5 changes: 3 additions & 2 deletions zstd/framedec.go
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Expand Up @@ -253,10 +253,11 @@ func (d *frameDec) reset(br byteBuffer) error {
return ErrWindowSizeTooSmall
}
d.history.windowSize = int(d.WindowSize)
if d.o.lowMem && d.history.windowSize < maxBlockSize {
if !d.o.lowMem || d.history.windowSize < maxBlockSize {
// Alloc 2x window size if not low-mem, or very small window size.
d.history.allocFrameBuffer = d.history.windowSize * 2
// TODO: Maybe use FrameContent size
} else {
// Alloc with one additional block
d.history.allocFrameBuffer = d.history.windowSize + maxBlockSize
}

Expand Down