From fe5a358aaeb7e582b763125c1e05e601ccad3b63 Mon Sep 17 00:00:00 2001 From: Cristian Staretu Date: Thu, 3 Jul 2014 09:40:53 +1000 Subject: [PATCH] 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://golang.org/cl/107440043 --- src/pkg/archive/tar/writer.go | 8 +++++--- 1 file changed, 5 insertions(+), 3 deletions(-) diff --git a/src/pkg/archive/tar/writer.go b/src/pkg/archive/tar/writer.go index 6eff6f6f84..d107dbbb51 100644 --- a/src/pkg/archive/tar/writer.go +++ b/src/pkg/archive/tar/writer.go @@ -37,8 +37,9 @@ type Writer struct { 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 @@ func (tw *Writer) writeHeader(hdr *Header, allowPax bool) error { // 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 -- 2.48.1