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Flatten backend.LimitedReadCloser structure 

This inlines the io.LimitedReader into the LimitedReadCloser body to
achieve fewer allocations. Results on linux/amd64:

name                                      old time/op    new time/op    delta
Backend/BenchmarkLoadPartialFile-8           412µs ± 4%     413µs ± 4%    ~     (p=0.634 n=17+17)
Backend/BenchmarkLoadPartialFileOffset-8     455µs ±13%     441µs ±10%    ~     (p=0.072 n=20+18)

name                                      old speed      new speed      delta
Backend/BenchmarkLoadPartialFile-8        10.2GB/s ± 3%  10.2GB/s ± 4%    ~     (p=0.817 n=16+17)
Backend/BenchmarkLoadPartialFileOffset-8  9.25GB/s ±12%  9.54GB/s ± 9%    ~     (p=0.072 n=20+18)

name                                      old alloc/op   new alloc/op   delta
Backend/BenchmarkLoadPartialFile-8            888B ± 0%      872B ± 0%  -1.80%  (p=0.000 n=15+15)
Backend/BenchmarkLoadPartialFileOffset-8      888B ± 0%      872B ± 0%  -1.80%  (p=0.000 n=15+15)

name                                      old allocs/op  new allocs/op  delta
Backend/BenchmarkLoadPartialFile-8            18.0 ± 0%      17.0 ± 0%  -5.56%  (p=0.000 n=15+15)
Backend/BenchmarkLoadPartialFileOffset-8      18.0 ± 0%      17.0 ± 0%  -5.56%  (p=0.000 n=15+15)
This commit is contained in:
greatroar 2020-05-26 13:35:07 +02:00
parent f4cd2a7120
commit 190d8e2f51
1 changed files with 4 additions and 9 deletions
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13
internal/backend/utils.go
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@ -32,19 +32,14 @@ func LoadAll(ctx context.Context, buf []byte, be restic.Backend, h restic.Handle
// LimitedReadCloser wraps io.LimitedReader and exposes the Close() method. // LimitedReadCloser wraps io.LimitedReader and exposes the Close() method.
type LimitedReadCloser struct { type LimitedReadCloser struct {
io.ReadCloser io.Closer
io.Reader io.LimitedReader
} }
// Read reads data from the limited reader. // LimitReadCloser returns a new reader wraps r in an io.LimitedReader, but also
func (l *LimitedReadCloser) Read(p []byte) (int, error) {
return l.Reader.Read(p)
}
// LimitReadCloser returns a new reader wraps r in an io.LimitReader, but also
// exposes the Close() method. // exposes the Close() method.
func LimitReadCloser(r io.ReadCloser, n int64) *LimitedReadCloser { func LimitReadCloser(r io.ReadCloser, n int64) *LimitedReadCloser {
return &LimitedReadCloser{ReadCloser: r, Reader: io.LimitReader(r, n)} return &LimitedReadCloser{Closer: r, LimitedReader: io.LimitedReader{R: r, N: n}}
} }
// DefaultLoad implements Backend.Load using lower-level openReader func // DefaultLoad implements Backend.Load using lower-level openReader func