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cmd/internal/obj, cmd/link: put all symbol data in one contiguous section

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Another object file change, gives a reasonable improvement:

name       old s/op   new s/op   delta
LinkCmdGo  0.46 ± 3%  0.44 ± 9%  -3.34%  (p=0.000 n=98+82)
LinkJuju   4.09 ± 4%  3.92 ± 5%  -4.30%  (p=0.000 n=98+99)

I guess the data section could be mmap-ed instead of read, I haven't tried
that.

Change-Id: I959eee470a05526ab1579e3f5d3ede41c16c954f
Reviewed-on: https://go-review.googlesource.com/20928
Run-TryBot: Michael Hudson-Doyle <michael.hudson@canonical.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: David Crawshaw <crawshaw@golang.org>
This commit is contained in:
Michael Hudson-Doyle 2016-03-21 10:55:20 +13:00
parent 34f0c0b3de
commit 36d5650a1c
3 changed files with 67 additions and 51 deletions
Download patch file Download diff file Expand all files Collapse all files

49
src/cmd/internal/obj/objfile.go
View file

@ -19,8 +19,10 @@
// - byte 1 - version number
// - sequence of strings giving dependencies (imported packages)
// - empty string (marks end of sequence)
// - sequence of sybol references used by the defined symbols
// - sequence of symbol references used by the defined symbols
// - byte 0xff (marks end of sequence)
// - integer (length of following data)
// - data, the content of the defined symbols
// - sequence of defined symbols
// - byte 0xff (marks end of sequence)
// - magic footer: "\xff\xffgo13ld"
@ -96,9 +98,6 @@
//
// TODO(rsc): The file format is good for a first pass but needs work.
// - There are SymID in the object file that should really just be strings.
// - The actual symbol memory images are interlaced with the symbol
// metadata. They should be separated, to reduce the I/O required to
// load just the metadata.
package obj
@ -319,15 +318,42 @@ func Writeobjfile(ctxt *Link, b *Biobuf) {
}
wrstring(b, "")
var dataLength int64
// Emit symbol references.
for _, s := range ctxt.Text {
writerefs(ctxt, b, s)
dataLength += int64(len(s.P))
pc := s.Pcln
dataLength += int64(len(pc.Pcsp.P))
dataLength += int64(len(pc.Pcfile.P))
dataLength += int64(len(pc.Pcline.P))
for i := 0; i < len(pc.Pcdata); i++ {
dataLength += int64(len(pc.Pcdata[i].P))
}
}
for _, s := range ctxt.Data {
writerefs(ctxt, b, s)
dataLength += int64(len(s.P))
}
Bputc(b, 0xff)
// Write data block
wrint(b, dataLength)
for _, s := range ctxt.Text {
b.w.Write(s.P)
pc := s.Pcln
b.w.Write(pc.Pcsp.P)
b.w.Write(pc.Pcfile.P)
b.w.Write(pc.Pcline.P)
for i := 0; i < len(pc.Pcdata); i++ {
b.w.Write(pc.Pcdata[i].P)
}
}
for _, s := range ctxt.Data {
b.w.Write(s.P)
}
// Emit symbols.
for _, s := range ctxt.Text {
writesym(ctxt, b, s)
@ -480,7 +506,7 @@ func writesym(ctxt *Link, b *Biobuf, s *LSym) {
wrint(b, flags)
wrint(b, s.Size)
wrsym(b, s.Gotype)
wrdata(b, s.P)
wrint(b, int64(len(s.P)))
wrint(b, int64(len(s.R)))
var r *Reloc
@ -521,12 +547,12 @@ func writesym(ctxt *Link, b *Biobuf, s *LSym) {
}
pc := s.Pcln
wrdata(b, pc.Pcsp.P)
wrdata(b, pc.Pcfile.P)
wrdata(b, pc.Pcline.P)
wrint(b, int64(len(pc.Pcsp.P)))
wrint(b, int64(len(pc.Pcfile.P)))
wrint(b, int64(len(pc.Pcline.P)))
wrint(b, int64(len(pc.Pcdata)))
for i := 0; i < len(pc.Pcdata); i++ {
wrdata(b, pc.Pcdata[i].P)
wrint(b, int64(len(pc.Pcdata[i].P)))
}
wrint(b, int64(len(pc.Funcdataoff)))
for i := 0; i < len(pc.Funcdataoff); i++ {
@ -564,11 +590,6 @@ func wrstring(b *Biobuf, s string) {
b.w.WriteString(s)
}
func wrdata(b *Biobuf, v []byte) {
wrint(b, int64(len(v)))
b.Write(v)
}
func wrsym(b *Biobuf, s *LSym) {
if s == nil {
wrint(b, 0)