Stowage/go
2
0
Fork 0
mirror of https://github.com/golang/go.git synced 2025-12-08 06:10:04 +00:00
Code Issues Projects Releases Packages Wiki Activity

[dev.link] cmd/link: emit ELF relocations in mmap

Browse source 
Currently, ELF relocations are generated sequentially in the heap
and flushed to output file periodically. In fact, in some cases,
the output size of the relocation records can be easily computed,
as a relocation entry has fixed size. We only need to count the
number of relocation records to compute the size.

Once the size is computed, we can mmap the output with the proper
size, and directly write relocation records in the mapped memory.
It also opens the possibility of writing relocations in parallel
(not done in this CL).

Note: on some architectures, a Go relocation may turn into
multiple ELF relocations, which makes size calculation harder.
This CL does not handle those cases, and it still writes
sequentially in the heap there.

Linking cmd/compile with external linking,

name          old time/op    new time/op    delta
Asmb2            190ms ± 2%     141ms ± 4%  -25.74%  (p=0.000 n=10+10)

name          old alloc/op   new alloc/op   delta
Asmb2_GC        66.8MB ± 0%     8.2MB ± 0%  -87.79%  (p=0.008 n=5+5)

name          old live-B     new live-B     delta
Asmb2_GC         66.9M ± 0%     55.2M ± 0%  -17.58%  (p=0.008 n=5+5)

Change-Id: If7056bbe909dc90033eef6b9c4891fcca310602c
Reviewed-on: https://go-review.googlesource.com/c/go/+/240399
Run-TryBot: Cherry Zhang <cherryyz@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Than McIntosh <thanm@google.com>
This commit is contained in:
Cherry Zhang 2020-06-26 16:35:49 -04:00
parent 364d320504
commit 987ce93824
13 changed files with 90 additions and 14 deletions
Download patch file Download diff file Expand all files Collapse all files

15
src/cmd/link/internal/ld/lib.go
View file

@ -236,12 +236,13 @@ type Arch struct {
Asmb func(*Link, *loader.Loader)
Asmb2 func(*Link, *loader.Loader)
Elfreloc1 func(*Link, *loader.Loader, loader.Sym, loader.ExtRelocView, int64) bool
Elfsetupplt func(ctxt *Link, plt, gotplt *loader.SymbolBuilder, dynamic loader.Sym)
Gentext func(*Link, *loader.Loader)
Machoreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtRelocView, int64) bool
PEreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtRelocView, int64) bool
Xcoffreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtRelocView, int64) bool
Elfreloc1 func(*Link, *loader.Loader, loader.Sym, loader.ExtRelocView, int64) bool
ElfrelocSize uint32 // size of an ELF relocation record, must match Elfreloc1. Currently this can be 0, meaning that the size is not fixed (a Go reloc may turn into multiple ELF reloc).
Elfsetupplt func(ctxt *Link, plt, gotplt *loader.SymbolBuilder, dynamic loader.Sym)
Gentext func(*Link, *loader.Loader)
Machoreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtRelocView, int64) bool
PEreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtRelocView, int64) bool
Xcoffreloc1 func(*sys.Arch, *OutBuf, *loader.Loader, loader.Sym, loader.ExtRelocView, int64) bool
// TLSIEtoLE converts a TLS Initial Executable relocation to
// a TLS Local Executable relocation.
@ -310,6 +311,8 @@ var (
Segrelrodata sym.Segment
Segdata sym.Segment
Segdwarf sym.Segment
Segments = []*sym.Segment{&Segtext, &Segrodata, &Segrelrodata, &Segdata, &Segdwarf}
)
const pkgdef = "__.PKGDEF"