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GC: avoid pathological behaviour; fixes #10040 [backport]

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This commit is contained in:
Andreas Rumpf
2018-12-20 08:20:32 +01:00
committed by narimiran
parent 90b4648a99
commit d02bf88f21
1 changed files with 8 additions and 9 deletions
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17
lib/system/gc.nim
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@@ -17,9 +17,9 @@
const
CycleIncrease = 2 # is a multiplicative increase
InitialCycleThreshold = 4*1024*1024 # X MB because cycle checking is slow
ZctThreshold = 500 # we collect garbage if the ZCT's size
# reaches this threshold
# this seems to be a good value
InitialZctThreshold = 500 # we collect garbage if the ZCT's size
# reaches this threshold
# this seems to be a good value
withRealTime = defined(useRealtimeGC)
when withRealTime and not declared(getTicks):
@@ -78,6 +78,7 @@ type
when nimCoroutines:
activeStack: ptr GcStack # current executing coroutine stack.
cycleThreshold: int
zctThreshold: int
when useCellIds:
idGenerator: int
zct: CellSeq # the zero count table
@@ -298,6 +299,7 @@ proc initGC() =
when traceGC:
for i in low(CellState)..high(CellState): init(states[i])
gch.cycleThreshold = InitialCycleThreshold
gch.zctThreshold = InitialZctThreshold
gch.stat.stackScans = 0
gch.stat.cycleCollections = 0
gch.stat.maxThreshold = 0
@@ -829,11 +831,7 @@ proc collectCTBody(gch: var GcHeap) =
c_fprintf(stdout, "[GC] missed deadline: %ld\n", duration)
proc collectCT(gch: var GcHeap) =
# stackMarkCosts prevents some pathological behaviour: Stack marking
# becomes more expensive with large stacks and large stacks mean that
# cells with RC=0 are more likely to be kept alive by the stack.
let stackMarkCosts = max(stackSize() div (16*sizeof(int)), ZctThreshold)
if (gch.zct.len >= stackMarkCosts or (cycleGC and
if (gch.zct.len >= gch.zctThreshold or (cycleGC and
getOccupiedMem(gch.region)>=gch.cycleThreshold) or alwaysGC) and
gch.recGcLock == 0:
when false:
@@ -841,6 +839,7 @@ proc collectCT(gch: var GcHeap) =
cellsetReset(gch.marked)
markForDebug(gch)
collectCTBody(gch)
gch.zctThreshold = max(InitialZctThreshold, gch.zct.len * CycleIncrease)
when withRealTime:
proc toNano(x: int): Nanos {.inline.} =
@@ -852,7 +851,7 @@ when withRealTime:
proc GC_step(gch: var GcHeap, us: int, strongAdvice: bool) =
acquire(gch)
gch.maxPause = us.toNano
if (gch.zct.len >= ZctThreshold or (cycleGC and
if (gch.zct.len >= gch.zctThreshold or (cycleGC and
getOccupiedMem(gch.region)>=gch.cycleThreshold) or alwaysGC) or
strongAdvice:
collectCTBody(gch)