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runtime: change p.runq from []*g to []guintptr

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This eliminates many write barriers in the scheduler code that are
unnecessary and will interfere with upcoming changes where the garbage
collector will have to invoke run queue functions in contexts that
must not have write barriers.

Change-Id: I702d0ac99cfd00ffff406e7362917db6a43e7e55
Reviewed-on: https://go-review.googlesource.com/16556
Reviewed-by: Russ Cox <rsc@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
This commit is contained in:
Austin Clements 2015-11-02 16:59:39 -05:00
parent 48155f5440
commit 0ca4488cc1
2 changed files with 8 additions and 8 deletions
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14
src/runtime/proc.go
View File

@ -3064,7 +3064,7 @@ func procresize(nprocs int32) *p {
for p.runqhead != p.runqtail { for p.runqhead != p.runqtail {
// pop from tail of local queue // pop from tail of local queue
p.runqtail-- p.runqtail--
gp := p.runq[p.runqtail%uint32(len(p.runq))] gp := p.runq[p.runqtail%uint32(len(p.runq))].ptr()
// push onto head of global queue // push onto head of global queue
globrunqputhead(gp) globrunqputhead(gp)
} }
@ -3753,7 +3753,7 @@ retry:
h := atomicload(&_p_.runqhead) // load-acquire, synchronize with consumers h := atomicload(&_p_.runqhead) // load-acquire, synchronize with consumers
t := _p_.runqtail t := _p_.runqtail
if t-h < uint32(len(_p_.runq)) { if t-h < uint32(len(_p_.runq)) {
_p_.runq[t%uint32(len(_p_.runq))] = gp _p_.runq[t%uint32(len(_p_.runq))].set(gp)
atomicstore(&_p_.runqtail, t+1) // store-release, makes the item available for consumption atomicstore(&_p_.runqtail, t+1) // store-release, makes the item available for consumption
return return
} }
@ -3776,7 +3776,7 @@ func runqputslow(_p_ *p, gp *g, h, t uint32) bool {
throw("runqputslow: queue is not full") throw("runqputslow: queue is not full")
} }
for i := uint32(0); i < n; i++ { for i := uint32(0); i < n; i++ {
batch[i] = _p_.runq[(h+i)%uint32(len(_p_.runq))] batch[i] = _p_.runq[(h+i)%uint32(len(_p_.runq))].ptr()
} }
if !cas(&_p_.runqhead, h, h+n) { // cas-release, commits consume if !cas(&_p_.runqhead, h, h+n) { // cas-release, commits consume
return false return false
@ -3824,7 +3824,7 @@ func runqget(_p_ *p) (gp *g, inheritTime bool) {
if t == h { if t == h {
return nil, false return nil, false
} }
gp := _p_.runq[h%uint32(len(_p_.runq))] gp := _p_.runq[h%uint32(len(_p_.runq))].ptr()
if cas(&_p_.runqhead, h, h+1) { // cas-release, commits consume if cas(&_p_.runqhead, h, h+1) { // cas-release, commits consume
return gp, false return gp, false
} }
@ -3835,7 +3835,7 @@ func runqget(_p_ *p) (gp *g, inheritTime bool) {
// Batch is a ring buffer starting at batchHead. // Batch is a ring buffer starting at batchHead.
// Returns number of grabbed goroutines. // Returns number of grabbed goroutines.
// Can be executed by any P. // Can be executed by any P.
func runqgrab(_p_ *p, batch *[256]*g, batchHead uint32, stealRunNextG bool) uint32 { func runqgrab(_p_ *p, batch *[256]guintptr, batchHead uint32, stealRunNextG bool) uint32 {
for { for {
h := atomicload(&_p_.runqhead) // load-acquire, synchronize with other consumers h := atomicload(&_p_.runqhead) // load-acquire, synchronize with other consumers
t := atomicload(&_p_.runqtail) // load-acquire, synchronize with the producer t := atomicload(&_p_.runqtail) // load-acquire, synchronize with the producer
@ -3856,7 +3856,7 @@ func runqgrab(_p_ *p, batch *[256]*g, batchHead uint32, stealRunNextG bool) uint
if !_p_.runnext.cas(next, 0) { if !_p_.runnext.cas(next, 0) {
continue continue
} }
batch[batchHead%uint32(len(batch))] = next.ptr() batch[batchHead%uint32(len(batch))] = next
return 1 return 1
} }
} }
@ -3885,7 +3885,7 @@ func runqsteal(_p_, p2 *p, stealRunNextG bool) *g {
return nil return nil
} }
n-- n--
gp := _p_.runq[(t+n)%uint32(len(_p_.runq))] gp := _p_.runq[(t+n)%uint32(len(_p_.runq))].ptr()
if n == 0 { if n == 0 {
return gp return gp
} }

2
src/runtime/runtime2.go
View File

@ -358,7 +358,7 @@ type p struct {
// Queue of runnable goroutines. Accessed without lock. // Queue of runnable goroutines. Accessed without lock.
runqhead uint32 runqhead uint32
runqtail uint32 runqtail uint32
runq [256]*g runq [256]guintptr
// runnext, if non-nil, is a runnable G that was ready'd by // runnext, if non-nil, is a runnable G that was ready'd by
// the current G and should be run next instead of what's in // the current G and should be run next instead of what's in
// runq if there's time remaining in the running G's time // runq if there's time remaining in the running G's time