diff options
| -rw-r--r-- | src/runtime/mgcsweep.go | 25 |
1 files changed, 22 insertions, 3 deletions
diff --git a/src/runtime/mgcsweep.go b/src/runtime/mgcsweep.go index c21ecc60d8..6ccf090ac5 100644 --- a/src/runtime/mgcsweep.go +++ b/src/runtime/mgcsweep.go @@ -873,11 +873,30 @@ func deductSweepCredit(spanBytes uintptr, callerSweepPages uintptr) { traceGCSweepStart() } + // Fix debt if necessary. retry: sweptBasis := mheap_.pagesSweptBasis.Load() - - // Fix debt if necessary. - newHeapLive := uintptr(gcController.heapLive.Load()-mheap_.sweepHeapLiveBasis) + spanBytes + live := gcController.heapLive.Load() + liveBasis := mheap_.sweepHeapLiveBasis + newHeapLive := spanBytes + if liveBasis < live { + // Only do this subtraction when we don't overflow. Otherwise, pagesTarget + // might be computed as something really huge, causing us to get stuck + // sweeping here until the next mark phase. + // + // Overflow can happen here if gcPaceSweeper is called concurrently with + // sweeping (i.e. not during a STW, like it usually is) because this code + // is intentionally racy. A concurrent call to gcPaceSweeper can happen + // if a GC tuning parameter is modified and we read an older value of + // heapLive than what was used to set the basis. + // + // This state should be transient, so it's fine to just let newHeapLive + // be a relatively small number. We'll probably just skip this attempt to + // sweep. + // + // See issue #57523. + newHeapLive += uintptr(live - liveBasis) + } pagesTarget := int64(mheap_.sweepPagesPerByte*float64(newHeapLive)) - int64(callerSweepPages) for pagesTarget > int64(mheap_.pagesSwept.Load()-sweptBasis) { if sweepone() == ^uintptr(0) { |