# HG changeset patch
# User Cristian Staretu <unclejacksons@gmail.com>
# Date 1404344453 -36000
# Thu Jul 03 09:40:53 2014 +1000
# Node ID 837348e418f33fc7a242f56dbe2feff829532526
# Parent c5f72a685e256457a0872f6587e2bb9500eac7c4
archive/tar: reuse temporary buffer in writeHeader
A temporary 512 bytes buffer is allocated for every call to
writeHeader. This buffer could be reused the lower the number
of memory allocations.
benchmark old ns/op new ns/op delta
BenchmarkWriteFiles100k 634622051 583810847 -8.01%
benchmark old allocs new allocs delta
BenchmarkWriteFiles100k 2701920 2602621 -3.68%
benchmark old bytes new bytes delta
BenchmarkWriteFiles100k 115383884 64349922 -44.23%
This change is very important if your code has to write a lot of
tarballs with a lot of files.
LGTM=dsymonds
R=golang-codereviews, dave, dsymonds
CC=golang-codereviews
https://codereview.appspot.com/107440043
Committer: David Symonds <dsymonds@golang.org>
diff -r c5f72a685e25 -r 837348e418f3 src/pkg/archive/tar/writer.go
--- a/src/pkg/archive/tar/writer.go Wed Jul 02 15:28:57 2014 -0700
+++ b/src/pkg/archive/tar/writer.go Thu Jul 03 09:40:53 2014 +1000
@@ -37,8 +37,9 @@
nb int64 // number of unwritten bytes for current file entry
pad int64 // amount of padding to write after current file entry
closed bool
- usedBinary bool // whether the binary numeric field extension was used
- preferPax bool // use pax header instead of binary numeric header
+ usedBinary bool // whether the binary numeric field extension was used
+ preferPax bool // use pax header instead of binary numeric header
+ hdrBuff [blockSize]byte // buffer to use in writeHeader
}
// NewWriter creates a new Writer writing to w.
@@ -160,7 +161,8 @@
// subsecond time resolution, but for now let's just capture
// too long fields or non ascii characters
- header := make([]byte, blockSize)
+ header := tw.hdrBuff[:]
+ copy(header, zeroBlock)
s := slicer(header)
// keep a reference to the filename to allow to overwrite it later if we detect that we can use ustar longnames instead of pax