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[dev.link] cmd/link/internal/loader: add 1-element object cache for use in toLocal

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To speed up the loader.Loader.toLocal() method, cache the index of the
most recently accessed object file and check that object's sym range
in toLocal() before doing a full binary search over all object symbol
ranges. This speeds up relink of kubernetes/hyperkube by about 2%, and
improves compilebench (relative to the dev.link branch) by about 5%:

name                      old time/op       new time/op       delta
LinkCompiler                    1.62s ± 8%        1.50s ± 9%  -7.21%  (p=0.000 n=20+19)
LinkWithoutDebugCompiler        1.13s ± 8%        1.09s ±12%    ~     (p=0.052 n=20+20)

name                      old user-time/op  new user-time/op  delta
LinkCompiler                    1.94s ±18%        1.97s ±16%    ~     (p=0.813 n=19+20)
LinkWithoutDebugCompiler        1.15s ±16%        1.13s ±12%    ~     (p=0.547 n=20+20)

Change-Id: Id5a8a847b533858373c0462f03972d436eda6748
Reviewed-on: https://go-review.googlesource.com/c/go/+/204337
Reviewed-by: Jeremy Faller <jeremy@golang.org>
Reviewed-by: Cherry Zhang <cherryyz@google.com>
This commit is contained in:
Than McIntosh 2019-10-30 10:14:33 -04:00
parent d77b809df9
commit e90e6e75f8
1 changed files with 9 additions and 2 deletions
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11
src/cmd/link/internal/loader/loader.go
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@ -65,6 +65,7 @@ type oReader struct {
type objIdx struct {
r *oReader
i Sym // start index
e Sym // end index
}
type nameVer struct {
@ -98,6 +99,7 @@ type Loader struct {
extStart Sym // from this index on, the symbols are externally defined
extSyms []nameVer // externally defined symbols
builtinSyms []Sym // global index of builtin symbols
ocache int // index (into 'objs') of most recent lookup
symsByName [2]map[string]Sym // map symbol name to index, two maps are for ABI0 and ABIInternal
extStaticSyms map[nameVer]Sym // externally defined static symbols, keyed by name
@ -116,7 +118,7 @@ func NewLoader() *Loader {
nbuiltin := goobj2.NBuiltin()
return &Loader{
start: make(map[*oReader]Sym),
objs: []objIdx{{nil, 0}},
objs: []objIdx{{nil, 0, 0}},
symsByName: [2]map[string]Sym{make(map[string]Sym), make(map[string]Sym)},
objByPkg: make(map[string]*oReader),
overwrite: make(map[Sym]Sym),
@ -143,7 +145,7 @@ func (l *Loader) addObj(pkg string, r *oReader) Sym {
n := r.NSym() + r.NNonpkgdef()
i := l.max + 1
l.start[r] = i
l.objs = append(l.objs, objIdx{r, i})
l.objs = append(l.objs, objIdx{r, i, i + Sym(n) - 1})
l.max += Sym(n)
return i
}
@ -249,12 +251,17 @@ func (l *Loader) toLocal(i Sym) (*oReader, int) {
if l.isExternal(i) {
return nil, int(i - l.extStart)
}
oc := l.ocache
if oc != 0 && i >= l.objs[oc].i && i <= l.objs[oc].e {
return l.objs[oc].r, int(i - l.objs[oc].i)
}
// Search for the local object holding index i.
// Below k is the first one that has its start index > i,
// so k-1 is the one we want.
k := sort.Search(len(l.objs), func(k int) bool {
return l.objs[k].i > i
})
l.ocache = k - 1
return l.objs[k-1].r, int(i - l.objs[k-1].i)
}