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runtime: update and access scavengeGoal atomically

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The first step toward acquiring the heap lock less frequently in the
scavenger.

Change-Id: Idc69fd8602be2c83268c155951230d60e20b42fe
Reviewed-on: https://go-review.googlesource.com/c/go/+/353973
Trust: Michael Knyszek <mknyszek@google.com>
Run-TryBot: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Go Bot <gobot@golang.org>
Reviewed-by: Michael Pratt <mpratt@google.com>
This commit is contained in:
Michael Anthony Knyszek 2021-10-04 19:52:48 +00:00 committed by Michael Knyszek
parent 9b2dd1f771
commit fc5e8cd6c9
2 changed files with 9 additions and 6 deletions
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8
src/runtime/mgcscavenge.go
View File

@ -125,7 +125,7 @@ func gcPaceScavenger(heapGoal, lastHeapGoal uint64) {
// information about the heap yet) so this is fine, and avoids a fault
// or garbage data later.
if lastHeapGoal == 0 {
mheap_.scavengeGoal = ^uint64(0)
atomic.Store64(&mheap_.scavengeGoal, ^uint64(0))
return
}
// Compute our scavenging goal.
@ -157,10 +157,10 @@ func gcPaceScavenger(heapGoal, lastHeapGoal uint64) {
// the background scavenger. We disable the background scavenger if there's
// less than one physical page of work to do because it's not worth it.
if retainedNow <= retainedGoal || retainedNow-retainedGoal < uint64(physPageSize) {
mheap_.scavengeGoal = ^uint64(0)
atomic.Store64(&mheap_.scavengeGoal, ^uint64(0))
return
}
mheap_.scavengeGoal = retainedGoal
atomic.Store64(&mheap_.scavengeGoal, retainedGoal)
}
// Sleep/wait state of the background scavenger.
@ -299,7 +299,7 @@ func bgscavenge(c chan int) {
lock(&mheap_.lock)
// If background scavenging is disabled or if there's no work to do just park.
retained, goal := heapRetained(), mheap_.scavengeGoal
retained, goal := heapRetained(), atomic.Load64(&mheap_.scavengeGoal)
if retained <= goal {
unlock(&mheap_.lock)
return

7
src/runtime/mheap.go
View File

@ -111,6 +111,8 @@ type mheap struct {
// scavengeGoal is the amount of total retained heap memory (measured by
// heapRetained) that the runtime will try to maintain by returning memory
// to the OS.
//
// Accessed atomically.
scavengeGoal uint64
// Page reclaimer state
@ -1399,9 +1401,10 @@ func (h *mheap) grow(npage uintptr) bool {
// By scavenging inline we deal with the failure to allocate out of
// memory fragments by scavenging the memory fragments that are least
// likely to be re-used.
if retained := heapRetained(); retained+uint64(totalGrowth) > h.scavengeGoal {
scavengeGoal := atomic.Load64(&h.scavengeGoal)
if retained := heapRetained(); retained+uint64(totalGrowth) > scavengeGoal {
todo := totalGrowth
if overage := uintptr(retained + uint64(totalGrowth) - h.scavengeGoal); todo > overage {
if overage := uintptr(retained + uint64(totalGrowth) - scavengeGoal); todo > overage {
todo = overage
}
h.pages.scavenge(todo, false)