Commit 64a26b79 authored by Austin Clements's avatar Austin Clements

runtime: simplify/optimize allocate-black a bit

Currently allocating black switches to the system stack (which is
probably a historical accident) and atomically updates the global
bytes marked stat. Since we're about to depend on this much more,
optimize it a bit by putting it back on the regular stack and updating
the per-P bytes marked stat, which gets lazily folded into the global
bytes marked stat.

Change-Id: Ibbe16e5382d3fd2256e4381f88af342bf7020b04
Reviewed-on: https://go-review.googlesource.com/22170Reviewed-by: default avatarRick Hudson <rlh@golang.org>
Run-TryBot: Austin Clements <austin@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
parent 479501c1
......@@ -695,9 +695,7 @@ func mallocgc(size uintptr, typ *_type, needzero bool) unsafe.Pointer {
// This may be racing with GC so do it atomically if there can be
// a race marking the bit.
if gcphase == _GCmarktermination || gcBlackenPromptly {
systemstack(func() {
gcmarknewobject_m(uintptr(x), size, scanSize)
})
gcmarknewobject(uintptr(x), size, scanSize)
}
if raceenabled {
......
......@@ -1132,15 +1132,20 @@ func gcDumpObject(label string, obj, off uintptr) {
}
}
// If gcBlackenPromptly is true we are in the second mark phase phase so we allocate black.
// gcmarknewobject marks a newly allocated object black. obj must
// not contain any non-nil pointers.
//
// This is nosplit so it can manipulate a gcWork without preemption.
//
//go:nowritebarrier
func gcmarknewobject_m(obj, size, scanSize uintptr) {
//go:nosplit
func gcmarknewobject(obj, size, scanSize uintptr) {
if useCheckmark && !gcBlackenPromptly { // The world should be stopped so this should not happen.
throw("gcmarknewobject called while doing checkmark")
}
heapBitsForAddr(obj).setMarked()
atomic.Xadd64(&work.bytesMarked, int64(size))
gcw := &getg().m.p.ptr().gcw
gcw.bytesMarked += uint64(size)
gcw.scanWork += int64(scanSize)
}
......
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