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# HG changeset patch
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# User Cristian Staretu <unclejacksons@gmail.com>
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# Date 1404344479 -36000
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# Thu Jul 03 09:41:19 2014 +1000
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# Node ID 17404efd6b02d4b3acd17070e3f89de97a145877
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# Parent 837348e418f33fc7a242f56dbe2feff829532526
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archive/tar: reuse temporary buffer in readHeader
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A temporary 512 bytes buffer is allocated for every call to
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readHeader. This buffer isn't returned to the caller and it could
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be reused to lower the number of memory allocations.
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This CL improves it by using a pool and zeroing out the buffer before
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putting it back into the pool.
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benchmark old ns/op new ns/op delta
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BenchmarkListFiles100k 545249903 538832687 -1.18%
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benchmark old allocs new allocs delta
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BenchmarkListFiles100k 2105167 2005692 -4.73%
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benchmark old bytes new bytes delta
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BenchmarkListFiles100k 105903472 54831527 -48.22%
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This improvement is very important if your code has to deal with a lot
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of tarballs which contain a lot of files.
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LGTM=dsymonds
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R=golang-codereviews, dave, dsymonds, bradfitz
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CC=golang-codereviews
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https://codereview.appspot.com/108240044
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Committer: David Symonds <dsymonds@golang.org>
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diff -r 837348e418f3 -r 17404efd6b02 src/pkg/archive/tar/reader.go
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--- a/src/pkg/archive/tar/reader.go Thu Jul 03 09:40:53 2014 +1000
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+++ b/src/pkg/archive/tar/reader.go Thu Jul 03 09:41:19 2014 +1000
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@@ -29,10 +29,11 @@
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// The Next method advances to the next file in the archive (including the first),
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// and then it can be treated as an io.Reader to access the file's data.
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type Reader struct {
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- r io.Reader
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- err error
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- pad int64 // amount of padding (ignored) after current file entry
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- curr numBytesReader // reader for current file entry
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+ r io.Reader
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+ err error
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+ pad int64 // amount of padding (ignored) after current file entry
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+ curr numBytesReader // reader for current file entry
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+ hdrBuff [blockSize]byte // buffer to use in readHeader
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}
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// A numBytesReader is an io.Reader with a numBytes method, returning the number
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@@ -426,7 +427,9 @@
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}
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func (tr *Reader) readHeader() *Header {
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- header := make([]byte, blockSize)
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+ header := tr.hdrBuff[:]
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+ copy(header, zeroBlock)
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+
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if _, tr.err = io.ReadFull(tr.r, header); tr.err != nil {
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return nil
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}
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