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runtime: split gfree list into with-stacks and without-stacks

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Currently all free Gs are added to one list. Split this into two
lists: one for free Gs with cached stacks and one for Gs without
cached stacks.

This lets us preferentially allocate Gs that already have a stack, but
more importantly, it sets us up to free cached G stacks concurrently.

Change-Id: Idbe486f708997e1c9d166662995283f02d1eeb3c
Reviewed-on: https://go-review.googlesource.com/20664
Reviewed-by: Rick Hudson <rlh@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
This commit is contained in:
Austin Clements 2016-03-11 16:27:51 -05:00
parent 3b0efa689e
commit 1a2cf91f5e
2 changed files with 30 additions and 11 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

34
src/runtime/proc.go
View File

@ -2798,8 +2798,13 @@ func gfput(_p_ *p, gp *g) {
_p_.gfreecnt--
gp = _p_.gfree
_p_.gfree = gp.schedlink.ptr()
gp.schedlink.set(sched.gfree)
sched.gfree = gp
if gp.stack.lo == 0 {
gp.schedlink.set(sched.gfreeNoStack)
sched.gfreeNoStack = gp
} else {
gp.schedlink.set(sched.gfreeStack)
sched.gfreeStack = gp
}
sched.ngfree++
}
unlock(&sched.gflock)
@ -2811,12 +2816,20 @@ func gfput(_p_ *p, gp *g) {
func gfget(_p_ *p) *g {
retry:
gp := _p_.gfree
if gp == nil && sched.gfree != nil {
if gp == nil && (sched.gfreeStack != nil || sched.gfreeNoStack != nil) {
lock(&sched.gflock)
for _p_.gfreecnt < 32 && sched.gfree != nil {
for _p_.gfreecnt < 32 {
if sched.gfreeStack != nil {
// Prefer Gs with stacks.
gp = sched.gfreeStack
sched.gfreeStack = gp.schedlink.ptr()
} else if sched.gfreeNoStack != nil {
gp = sched.gfreeNoStack
sched.gfreeNoStack = gp.schedlink.ptr()
} else {
break
}
_p_.gfreecnt++
gp = sched.gfree
sched.gfree = gp.schedlink.ptr()
sched.ngfree--
gp.schedlink.set(_p_.gfree)
_p_.gfree = gp
@ -2853,8 +2866,13 @@ func gfpurge(_p_ *p) {
_p_.gfreecnt--
gp := _p_.gfree
_p_.gfree = gp.schedlink.ptr()
gp.schedlink.set(sched.gfree)
sched.gfree = gp
if gp.stack.lo == 0 {
gp.schedlink.set(sched.gfreeNoStack)
sched.gfreeNoStack = gp
} else {
gp.schedlink.set(sched.gfreeStack)
sched.gfreeStack = gp
}
sched.ngfree++
}
unlock(&sched.gflock)

7
src/runtime/runtime2.go
View File

@ -523,9 +523,10 @@ type schedt struct {
runqsize int32
// Global cache of dead G's.
gflock mutex
gfree *g
ngfree int32
gflock mutex
gfreeStack *g
gfreeNoStack *g
ngfree int32
// Central cache of sudog structs.
sudoglock mutex