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runtime: remove mcache field from m

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Having an mcache field in both m and p is confusing, so remove it from m.
Always use mcache field from p. Use new variable mcache0 during bootstrap.

Change-Id: If2cba9f8bb131d911d512b61fd883a86cf62cc98
Reviewed-on: https://go-review.googlesource.com/c/go/+/205239
Run-TryBot: Ian Lance Taylor <iant@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
This commit is contained in:
Ian Lance Taylor 2019-11-04 14:25:22 -08:00
parent 7802b55176
commit 3093959ee1
7 changed files with 54 additions and 43 deletions
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19
src/runtime/malloc.go
View File

@ -468,8 +468,7 @@ func mallocinit() {
// Initialize the heap.
mheap_.init()
_g_ := getg()
_g_.m.mcache = allocmcache()
mcache0 = allocmcache()
// Create initial arena growth hints.
if sys.PtrSize == 8 {
@ -953,7 +952,19 @@ func mallocgc(size uintptr, typ *_type, needzero bool) unsafe.Pointer {
shouldhelpgc := false
dataSize := size
c := gomcache()
var c *mcache
if mp.p != 0 {
c = mp.p.ptr().mcache
} else {
// We will be called without a P while bootstrapping,
// in which case we use mcache0, which is set in mallocinit.
// mcache0 is cleared when bootstrapping is complete,
// by procresize.
c = mcache0
if c == nil {
throw("malloc called with no P")
}
}
var x unsafe.Pointer
noscan := typ == nil || typ.ptrdata == 0
if size <= maxSmallSize {
@ -1193,7 +1204,7 @@ func reflect_unsafe_NewArray(typ *_type, n int) unsafe.Pointer {
}
func profilealloc(mp *m, x unsafe.Pointer, size uintptr) {
mp.mcache.next_sample = nextSample()
mp.p.ptr().mcache.next_sample = nextSample()
mProf_Malloc(x, size)
}

2
src/runtime/mgcsweep.go
View File

@ -226,7 +226,7 @@ func (s *mspan) sweep(preserve bool) bool {
size := s.elemsize
res := false
c := _g_.m.mcache
c := _g_.m.p.ptr().mcache
freeToHeap := false
// The allocBits indicate which unmarked objects don't need to be

29
src/runtime/mheap.go
View File

@ -1141,10 +1141,21 @@ func (h *mheap) allocSpan(npages uintptr, manual bool, spanclass spanClass, sysS
// which may only be done with the heap locked.
// Transfer stats from mcache to global.
memstats.heap_scan += uint64(gp.m.mcache.local_scan)
gp.m.mcache.local_scan = 0
memstats.tinyallocs += uint64(gp.m.mcache.local_tinyallocs)
gp.m.mcache.local_tinyallocs = 0
var c *mcache
if gp.m.p != 0 {
c = gp.m.p.ptr().mcache
} else {
// This case occurs while bootstrapping.
// See the similar code in mallocgc.
c = mcache0
if c == nil {
throw("mheap.allocSpan called with no P")
}
}
memstats.heap_scan += uint64(c.local_scan)
c.local_scan = 0
memstats.tinyallocs += uint64(c.local_tinyallocs)
c.local_tinyallocs = 0
// Do some additional accounting if it's a large allocation.
if spanclass.sizeclass() == 0 {
@ -1342,12 +1353,12 @@ func (h *mheap) grow(npage uintptr) bool {
// Free the span back into the heap.
func (h *mheap) freeSpan(s *mspan) {
systemstack(func() {
mp := getg().m
c := getg().m.p.ptr().mcache
lock(&h.lock)
memstats.heap_scan += uint64(mp.mcache.local_scan)
mp.mcache.local_scan = 0
memstats.tinyallocs += uint64(mp.mcache.local_tinyallocs)
mp.mcache.local_tinyallocs = 0
memstats.heap_scan += uint64(c.local_scan)
c.local_scan = 0
memstats.tinyallocs += uint64(c.local_tinyallocs)
c.local_tinyallocs = 0
if msanenabled {
// Tell msan that this entire span is no longer in use.
base := unsafe.Pointer(s.base())

29
src/runtime/proc.go
View File

@ -82,6 +82,7 @@ var modinfo string
var (
m0 m
g0 g
mcache0 *mcache
raceprocctx0 uintptr
)
@ -2957,7 +2958,6 @@ func reentersyscall(pc, sp uintptr) {
_g_.m.syscalltick = _g_.m.p.ptr().syscalltick
_g_.sysblocktraced = true
_g_.m.mcache = nil
pp := _g_.m.p.ptr()
pp.m = 0
_g_.m.oldp.set(pp)
@ -3083,9 +3083,6 @@ func exitsyscall() {
oldp := _g_.m.oldp.ptr()
_g_.m.oldp = 0
if exitsyscallfast(oldp) {
if _g_.m.mcache == nil {
throw("lost mcache")
}
if trace.enabled {
if oldp != _g_.m.p.ptr() || _g_.m.syscalltick != _g_.m.p.ptr().syscalltick {
systemstack(traceGoStart)
@ -3136,10 +3133,6 @@ func exitsyscall() {
// Call the scheduler.
mcall(exitsyscall0)
if _g_.m.mcache == nil {
throw("lost mcache")
}
// Scheduler returned, so we're allowed to run now.
// Delete the syscallsp information that we left for
// the garbage collector during the system call.
@ -4033,10 +4026,12 @@ func (pp *p) init(id int32) {
pp.wbBuf.reset()
if pp.mcache == nil {
if id == 0 {
if getg().m.mcache == nil {
if mcache0 == nil {
throw("missing mcache?")
}
pp.mcache = getg().m.mcache // bootstrap
// Use the bootstrap mcache0. Only one P will get
// mcache0: the one with ID 0.
pp.mcache = mcache0
} else {
pp.mcache = allocmcache()
}
@ -4216,7 +4211,6 @@ func procresize(nprocs int32) *p {
_g_.m.p.ptr().m = 0
}
_g_.m.p = 0
_g_.m.mcache = nil
p := allp[0]
p.m = 0
p.status = _Pidle
@ -4226,6 +4220,9 @@ func procresize(nprocs int32) *p {
}
}
// g.m.p is now set, so we no longer need mcache0 for bootstrapping.
mcache0 = nil
// release resources from unused P's
for i := nprocs; i < old; i++ {
p := allp[i]
@ -4291,7 +4288,7 @@ func acquirep(_p_ *p) {
func wirep(_p_ *p) {
_g_ := getg()
if _g_.m.p != 0 || _g_.m.mcache != nil {
if _g_.m.p != 0 {
throw("wirep: already in go")
}
if _p_.m != 0 || _p_.status != _Pidle {
@ -4302,7 +4299,6 @@ func wirep(_p_ *p) {
print("wirep: p->m=", _p_.m, "(", id, ") p->status=", _p_.status, "\n")
throw("wirep: invalid p state")
}
_g_.m.mcache = _p_.mcache
_g_.m.p.set(_p_)
_p_.m.set(_g_.m)
_p_.status = _Prunning
@ -4312,19 +4308,18 @@ func wirep(_p_ *p) {
func releasep() *p {
_g_ := getg()
if _g_.m.p == 0 || _g_.m.mcache == nil {
if _g_.m.p == 0 {
throw("releasep: invalid arg")
}
_p_ := _g_.m.p.ptr()
if _p_.m.ptr() != _g_.m || _p_.mcache != _g_.m.mcache || _p_.status != _Prunning {
print("releasep: m=", _g_.m, " m->p=", _g_.m.p.ptr(), " p->m=", hex(_p_.m), " m->mcache=", _g_.m.mcache, " p->mcache=", _p_.mcache, " p->status=", _p_.status, "\n")
if _p_.m.ptr() != _g_.m || _p_.status != _Prunning {
print("releasep: m=", _g_.m, " m->p=", _g_.m.p.ptr(), " p->m=", hex(_p_.m), " p->status=", _p_.status, "\n")
throw("releasep: invalid p state")
}
if trace.enabled {
traceProcStop(_g_.m.p.ptr())
}
_g_.m.p = 0
_g_.m.mcache = nil
_p_.m = 0
_p_.status = _Pidle
return _p_

5
src/runtime/runtime1.go
View File

@ -459,11 +459,6 @@ func releasem(mp *m) {
}
}
//go:nosplit
func gomcache() *mcache {
return getg().m.mcache
}
//go:linkname reflect_typelinks reflect.typelinks
func reflect_typelinks() ([]unsafe.Pointer, [][]int32) {
modules := activeModules()

1
src/runtime/runtime2.go
View File

@ -510,7 +510,6 @@ type m struct {
park note
alllink *m // on allm
schedlink muintptr
mcache *mcache
lockedg guintptr
createstack [32]uintptr // stack that created this thread.
lockedExt uint32 // tracking for external LockOSThread

12
src/runtime/stack.go
View File

@ -357,16 +357,16 @@ func stackalloc(n uint32) stack {
n2 >>= 1
}
var x gclinkptr
c := thisg.m.mcache
if stackNoCache != 0 || c == nil || thisg.m.preemptoff != "" {
// c == nil can happen in the guts of exitsyscall or
// procresize. Just get a stack from the global pool.
if stackNoCache != 0 || thisg.m.p == 0 || thisg.m.preemptoff != "" {
// thisg.m.p == 0 can happen in the guts of exitsyscall
// or procresize. Just get a stack from the global pool.
// Also don't touch stackcache during gc
// as it's flushed concurrently.
lock(&stackpool[order].item.mu)
x = stackpoolalloc(order)
unlock(&stackpool[order].item.mu)
} else {
c := thisg.m.p.ptr().mcache
x = c.stackcache[order].list
if x.ptr() == nil {
stackcacherefill(c, order)
@ -452,12 +452,12 @@ func stackfree(stk stack) {
n2 >>= 1
}
x := gclinkptr(v)
c := gp.m.mcache
if stackNoCache != 0 || c == nil || gp.m.preemptoff != "" {
if stackNoCache != 0 || gp.m.p == 0 || gp.m.preemptoff != "" {
lock(&stackpool[order].item.mu)
stackpoolfree(x, order)
unlock(&stackpool[order].item.mu)
} else {
c := gp.m.p.ptr().mcache
if c.stackcache[order].size >= _StackCacheSize {
stackcacherelease(c, order)
}