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runtime: factor out GC assist credit accounting

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No-op change in preparation for arenas.

For #51317.

Change-Id: I0777f21763fcd34957b7e709580cf2b7a962ba67
Reviewed-on: https://go-review.googlesource.com/c/go/+/423365
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
This commit is contained in:
Michael Anthony Knyszek 2022-08-13 16:37:09 +00:00 committed by Michael Knyszek
parent 69fc74f3ee
commit 987f94fa03
1 changed files with 29 additions and 18 deletions
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47
src/runtime/malloc.go
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@ -895,24 +895,7 @@ func mallocgc(size uintptr, typ *_type, needzero bool) unsafe.Pointer {
// assistG is the G to charge for this allocation, or nil if
// GC is not currently active.
var assistG *g
if gcBlackenEnabled != 0 {
// Charge the current user G for this allocation.
assistG = getg()
if assistG.m.curg != nil {
assistG = assistG.m.curg
}
// Charge the allocation against the G. We'll account
// for internal fragmentation at the end of mallocgc.
assistG.gcAssistBytes -= int64(size)
if assistG.gcAssistBytes < 0 {
// This G is in debt. Assist the GC to correct
// this before allocating. This must happen
// before disabling preemption.
gcAssistAlloc(assistG)
}
}
assistG := deductAssistCredit(size)
// Set mp.mallocing to keep from being preempted by GC.
mp := acquirem()
@ -1165,6 +1148,34 @@ func mallocgc(size uintptr, typ *_type, needzero bool) unsafe.Pointer {
return x
}
// deductAssistCredit reduces the current G's assist credit
// by size bytes, and assists the GC if necessary.
//
// Caller must be preemptible.
//
// Returns the G for which the assist credit was accounted.
func deductAssistCredit(size uintptr) *g {
var assistG *g
if gcBlackenEnabled != 0 {
// Charge the current user G for this allocation.
assistG = getg()
if assistG.m.curg != nil {
assistG = assistG.m.curg
}
// Charge the allocation against the G. We'll account
// for internal fragmentation at the end of mallocgc.
assistG.gcAssistBytes -= int64(size)
if assistG.gcAssistBytes < 0 {
// This G is in debt. Assist the GC to correct
// this before allocating. This must happen
// before disabling preemption.
gcAssistAlloc(assistG)
}
}
return assistG
}
// memclrNoHeapPointersChunked repeatedly calls memclrNoHeapPointers
// on chunks of the buffer to be zeroed, with opportunities for preemption
// along the way. memclrNoHeapPointers contains no safepoints and also