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runtime: clean up old mcentral code

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This change deletes the old mcentral implementation from the code base
and the newMCentralImpl feature flag along with it.

Updates #37487.

Change-Id: Ibca8f722665f0865051f649ffe699cbdbfdcfcf2
Reviewed-on: https://go-review.googlesource.com/c/go/+/221184
Run-TryBot: Michael Knyszek <mknyszek@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Austin Clements <austin@google.com>
Reviewed-by: Michael Pratt <mpratt@google.com>
This commit is contained in:
Michael Anthony Knyszek 2020-02-19 16:37:48 +00:00 • committed by Michael Knyszek
parent 260dff3ca3
commit e6d0bd2b89
8 changed files with 25 additions and 665 deletions
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36
src/runtime/mheap.go
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@ -44,15 +44,6 @@ const (
// Must be a multiple of the pageInUse bitmap element size and
// must also evenly divid pagesPerArena.
pagesPerReclaimerChunk = 512
// go115NewMCentralImpl is a feature flag for the new mcentral implementation.
//
// This flag depends on go115NewMarkrootSpans because the new mcentral
// implementation requires that markroot spans no longer rely on mgcsweepbufs.
// The definition of this flag helps ensure that if there's a problem with
// the new markroot spans implementation and it gets turned off, that the new
// mcentral implementation also gets turned off so the runtime isn't broken.
go115NewMCentralImpl = true
)
// Main malloc heap.
@ -85,19 +76,6 @@ type mheap struct {
// access (since that may free the backing store).
allspans []*mspan // all spans out there
// sweepSpans contains two mspan stacks: one of swept in-use
// spans, and one of unswept in-use spans. These two trade
// roles on each GC cycle. Since the sweepgen increases by 2
// on each cycle, this means the swept spans are in
// sweepSpans[sweepgen/2%2] and the unswept spans are in
// sweepSpans[1-sweepgen/2%2]. Sweeping pops spans from the
// unswept stack and pushes spans that are still in-use on the
// swept stack. Likewise, allocating an in-use span pushes it
// on the swept stack.
//
// For !go115NewMCentralImpl.
sweepSpans [2]gcSweepBuf
_ uint32 // align uint64 fields on 32-bit for atomics
// Proportional sweep
@ -220,7 +198,7 @@ type mheap struct {
base, end uintptr
}
// _ uint32 // ensure 64-bit alignment of central
_ uint32 // ensure 64-bit alignment of central
// central free lists for small size classes.
// the padding makes sure that the mcentrals are
@ -719,8 +697,6 @@ func pageIndexOf(p uintptr) (arena *heapArena, pageIdx uintptr, pageMask uint8)
// Initialize the heap.
func (h *mheap) init() {
lockInit(&h.lock, lockRankMheap)
lockInit(&h.sweepSpans[0].spineLock, lockRankSpine)
lockInit(&h.sweepSpans[1].spineLock, lockRankSpine)
lockInit(&h.speciallock, lockRankMheapSpecial)
h.spanalloc.init(unsafe.Sizeof(mspan{}), recordspan, unsafe.Pointer(h), &memstats.mspan_sys)
@ -1294,16 +1270,6 @@ HaveSpan:
h.setSpans(s.base(), npages, s)
if !manual {
if !go115NewMCentralImpl {
// Add to swept in-use list.
//
// This publishes the span to root marking.
//
// h.sweepgen is guaranteed to only change during STW,
// and preemption is disabled in the page allocator.
h.sweepSpans[h.sweepgen/2%2].push(s)
}
// Mark in-use span in arena page bitmap.
//
// This publishes the span to the page sweeper, so