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runtime: combine gcWorkProducer into gcWork

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The distinction between gcWorkProducer and gcWork (producer and
consumer) is not serving us as originally intended, so merge these
into just gcWork.

The original intent was to replace the currentwbuf cache with a
gcWorkProducer. However, with gchelpwork (aka mutator assists),
mutators can both produce and consume work, so it will make more sense
to cache a whole gcWork.

Change-Id: I6e633e96db7cb23a64fbadbfc4607e3ad32bcfb3
Reviewed-on: https://go-review.googlesource.com/7733
Reviewed-by: Rick Hudson <rlh@golang.org>
This commit is contained in:
Austin Clements 2015-03-12 13:09:30 -04:00
parent 77fcf36a5e
commit cadd4f81a8
2 changed files with 34 additions and 58 deletions
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18
src/runtime/mgcmark.go
View File

@ -55,7 +55,7 @@ var oneptr = [...]uint8{typePointer}
//go:nowritebarrier
func markroot(desc *parfor, i uint32) {
var gcw gcWorkProducer
var gcw gcWork
// Note: if you add a case here, please also update heapdump.go:dumproots.
switch i {
@ -246,7 +246,7 @@ func scanstack(gp *g) {
throw("can't scan gchelper stack")
}
var gcw gcWorkProducer
var gcw gcWork
gcw.initFromCache()
scanframe := func(frame *stkframe, unused unsafe.Pointer) bool {
// Pick up gcw as free variable so gentraceback and friends can
@ -262,7 +262,7 @@ func scanstack(gp *g) {
// Scan a stack frame: local variables and function arguments/results.
//go:nowritebarrier
func scanframeworker(frame *stkframe, unused unsafe.Pointer, gcw *gcWorkProducer) {
func scanframeworker(frame *stkframe, unused unsafe.Pointer, gcw *gcWork) {
f := frame.fn
targetpc := frame.continpc
@ -360,7 +360,7 @@ func gcDrain(gcw *gcWork) {
// out of the wbuf passed in + a single object placed
// into an empty wbuf in scanobject so there could be
// a performance hit as we keep fetching fresh wbufs.
scanobject(b, 0, nil, &gcw.gcWorkProducer)
scanobject(b, 0, nil, gcw)
}
checknocurrentwbuf()
}
@ -378,14 +378,14 @@ func gcDrainN(gcw *gcWork, n int) {
if b == 0 {
return
}
scanobject(b, 0, nil, &gcw.gcWorkProducer)
scanobject(b, 0, nil, gcw)
}
}
// scanblock scans b as scanobject would.
// If the gcphase is GCscan, scanblock performs additional checks.
//go:nowritebarrier
func scanblock(b0, n0 uintptr, ptrmask *uint8, gcw *gcWorkProducer) {
func scanblock(b0, n0 uintptr, ptrmask *uint8, gcw *gcWork) {
// Use local copies of original parameters, so that a stack trace
// due to one of the throws below shows the original block
// base and extent.
@ -411,7 +411,7 @@ func scanblock(b0, n0 uintptr, ptrmask *uint8, gcw *gcWorkProducer) {
// In this case, n may be an overestimate of the size; the GC bitmap
// must also be used to make sure the scan stops at the end of b.
//go:nowritebarrier
func scanobject(b, n uintptr, ptrmask *uint8, gcw *gcWorkProducer) {
func scanobject(b, n uintptr, ptrmask *uint8, gcw *gcWork) {
arena_start := mheap_.arena_start
arena_used := mheap_.arena_used
@ -489,7 +489,7 @@ func shade(b uintptr) {
// throw("shade during harvest")
// }
var gcw gcWorkProducer
var gcw gcWork
greyobject(obj, 0, 0, hbits, &gcw)
// This is part of the write barrier so put the wbuf back.
if gcphase == _GCmarktermination {
@ -512,7 +512,7 @@ func shade(b uintptr) {
// Return possibly new workbuf to use.
// base and off are for debugging only and could be removed.
//go:nowritebarrier
func greyobject(obj, base, off uintptr, hbits heapBits, gcw *gcWorkProducer) {
func greyobject(obj, base, off uintptr, hbits heapBits, gcw *gcWork) {
// obj should be start of allocation, and so must be at least pointer-aligned.
if obj&(ptrSize-1) != 0 {
throw("greyobject: obj not pointer-aligned")

74
src/runtime/mgcwork.go
View File

@ -35,36 +35,25 @@ func (wp wbufptr) ptr() *workbuf {
return (*workbuf)(unsafe.Pointer(wp))
}
// A gcWorkProducer provides the interface to produce work for the
// A gcWork provides the interface to produce and consume work for the
// garbage collector.
//
// The usual pattern for using gcWorkProducer is:
// The usual pattern for using gcWork is:
//
// var gcw gcWorkProducer
// .. call gcw.put() ..
// var gcw gcWork
// .. call gcw.put() to produce and gcw.get() to consume ..
// gcw.dispose()
type gcWorkProducer struct {
type gcWork struct {
// Invariant: wbuf is never full or empty
wbuf wbufptr
}
// A gcWork provides the interface to both produce and consume work
// for the garbage collector.
//
// The pattern for using gcWork is the same as gcWorkProducer.
type gcWork struct {
gcWorkProducer
}
// Note that there is no need for a gcWorkConsumer because everything
// that consumes pointers also produces them.
// initFromCache fetches work from this M's currentwbuf cache.
//go:nowritebarrier
func (w *gcWorkProducer) initFromCache() {
// TODO: Instead of making gcWorkProducer pull from the
// currentwbuf cache, use a gcWorkProducer as the cache and
// make shade pass around that gcWorkProducer.
func (w *gcWork) initFromCache() {
// TODO: Instead of making gcWork pull from the currentwbuf
// cache, use a gcWork as the cache and make shade pass around
// that gcWork.
if w.wbuf == 0 {
w.wbuf = wbufptr(xchguintptr(&getg().m.currentwbuf, 0))
}
@ -72,8 +61,8 @@ func (w *gcWorkProducer) initFromCache() {
// put enqueues a pointer for the garbage collector to trace.
//go:nowritebarrier
func (ww *gcWorkProducer) put(obj uintptr) {
w := (*gcWorkProducer)(noescape(unsafe.Pointer(ww))) // TODO: remove when escape analysis is fixed
func (ww *gcWork) put(obj uintptr) {
w := (*gcWork)(noescape(unsafe.Pointer(ww))) // TODO: remove when escape analysis is fixed
wbuf := w.wbuf.ptr()
if wbuf == nil {
@ -90,28 +79,6 @@ func (ww *gcWorkProducer) put(obj uintptr) {
}
}
// dispose returns any cached pointers to the global queue.
//go:nowritebarrier
func (w *gcWorkProducer) dispose() {
if wbuf := w.wbuf; wbuf != 0 {
putpartial(wbuf.ptr(), 58)
w.wbuf = 0
}
}
// disposeToCache returns any cached pointers to this M's currentwbuf.
// It calls throw if currentwbuf is non-nil.
//go:nowritebarrier
func (w *gcWorkProducer) disposeToCache() {
if wbuf := w.wbuf; wbuf != 0 {
wbuf = wbufptr(xchguintptr(&getg().m.currentwbuf, uintptr(wbuf)))
if wbuf != 0 {
throw("m.currentwbuf non-nil in disposeToCache")
}
w.wbuf = 0
}
}
// tryGet dequeues a pointer for the garbage collector to trace.
//
// If there are no pointers remaining in this gcWork or in the global
@ -175,11 +142,20 @@ func (ww *gcWork) get() uintptr {
//go:nowritebarrier
func (w *gcWork) dispose() {
if wbuf := w.wbuf; wbuf != 0 {
// Even though wbuf may only be partially full, we
// want to keep it on the consumer's queues rather
// than putting it back on the producer's queues.
// Hence, we use putfull here.
putfull(wbuf.ptr(), 133)
putpartial(wbuf.ptr(), 167)
w.wbuf = 0
}
}
// disposeToCache returns any cached pointers to this M's currentwbuf.
// It calls throw if currentwbuf is non-nil.
//go:nowritebarrier
func (w *gcWork) disposeToCache() {
if wbuf := w.wbuf; wbuf != 0 {
wbuf = wbufptr(xchguintptr(&getg().m.currentwbuf, uintptr(wbuf)))
if wbuf != 0 {
throw("m.currentwbuf non-nil in disposeToCache")
}
w.wbuf = 0
}
}