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Remove GC (#21904)

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* .

* Remove GC v2
This commit is contained in:
Juan Carlos
2023-05-25 02:06:31 -03:00
committed by GitHub
parent 446e5fbbb3
commit b7925bf5c9
1 changed files with 0 additions and 749 deletions
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lib/system/gc2.nim
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#
#
# Nim's Runtime Library
# (c) Copyright 2017 Andreas Rumpf
#
# See the file "copying.txt", included in this
# distribution, for details about the copyright.
#
# xxx deadcode, consider removing unless something could be reused.
# Garbage Collector
#
# The basic algorithm is an incremental mark
# and sweep GC to free cycles. It is hard realtime in that if you play
# according to its rules, no deadline will ever be missed.
# Since this kind of collector is very bad at recycling dead objects
# early, Nim's codegen emits ``nimEscape`` calls at strategic
# places. For this to work even 'unsureAsgnRef' needs to mark things
# so that only return values need to be considered in ``nimEscape``.
{.push profiler:off.}
const
CycleIncrease = 2 # is a multiplicative increase
InitialCycleThreshold = 512*1024 # start collecting after 500KB
ZctThreshold = 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):
include "system/timers"
when defined(memProfiler):
proc nimProfile(requestedSize: int) {.benign.}
when hasThreadSupport:
include sharedlist
type
ObjectSpaceIter = object
state: range[-1..0]
iterToProc(allObjects, ptr ObjectSpaceIter, allObjectsAsProc)
const
escapedBit = 0b1000 # so that lowest 3 bits are not touched
rcBlackOrig = 0b000
rcWhiteOrig = 0b001
rcGrey = 0b010 # traditional color for incremental mark&sweep
rcUnused = 0b011
colorMask = 0b011
type
WalkOp = enum
waMarkGlobal, # part of the backup mark&sweep
waMarkGrey,
waZctDecRef,
waDebug
Phase {.pure.} = enum
None, Marking, Sweeping
Finalizer {.compilerproc.} = proc (self: pointer) {.nimcall, benign.}
# A ref type can have a finalizer that is called before the object's
# storage is freed.
GcStat = object
stackScans: int # number of performed stack scans (for statistics)
completedCollections: int # number of performed full collections
maxThreshold: int # max threshold that has been set
maxStackSize: int # max stack size
maxStackCells: int # max stack cells in ``decStack``
cycleTableSize: int # max entries in cycle table
maxPause: int64 # max measured GC pause in nanoseconds
GcStack {.final, pure.} = object
when nimCoroutines:
prev: ptr GcStack
next: ptr GcStack
maxStackSize: int # Used to track statistics because we can not use
# GcStat.maxStackSize when multiple stacks exist.
bottom: pointer
when withRealTime or nimCoroutines:
pos: pointer # Used with `withRealTime` only for code clarity, see GC_Step().
when withRealTime:
bottomSaved: pointer
GcHeap = object # this contains the zero count and
# non-zero count table
black, red: int # either 0 or 1.
stack: GcStack
when nimCoroutines:
activeStack: ptr GcStack # current executing coroutine stack.
phase: Phase
cycleThreshold: int
when useCellIds:
idGenerator: int
greyStack: CellSeq
recGcLock: int # prevent recursion via finalizers; no thread lock
when withRealTime:
maxPause: Nanos # max allowed pause in nanoseconds; active if > 0
region: MemRegion # garbage collected region
stat: GcStat
additionalRoots: CellSeq # explicit roots for GC_ref/unref
spaceIter: ObjectSpaceIter
pDumpHeapFile: pointer # File that is used for GC_dumpHeap
when hasThreadSupport:
toDispose: SharedList[pointer]
gcThreadId: int
var
gch {.rtlThreadVar.}: GcHeap
when not defined(useNimRtl):
instantiateForRegion(gch.region)
# Which color to use for new objects is tricky: When we're marking,
# they have to be *white* so that everything is marked that is only
# reachable from them. However, when we are sweeping, they have to
# be black, so that we don't free them prematuredly. In order to save
# a comparison gch.phase == Phase.Marking, we use the pseudo-color
# 'red' for new objects.
template allocColor(): untyped = gch.red
template gcAssert(cond: bool, msg: string) =
when defined(useGcAssert):
if not cond:
echo "[GCASSERT] ", msg
GC_disable()
writeStackTrace()
rawQuit 1
proc cellToUsr(cell: PCell): pointer {.inline.} =
# convert object (=pointer to refcount) to pointer to userdata
result = cast[pointer](cast[int](cell)+%ByteAddress(sizeof(Cell)))
proc usrToCell(usr: pointer): PCell {.inline.} =
# convert pointer to userdata to object (=pointer to refcount)
result = cast[PCell](cast[int](usr)-%ByteAddress(sizeof(Cell)))
proc extGetCellType(c: pointer): PNimType {.compilerproc.} =
# used for code generation concerning debugging
result = usrToCell(c).typ
proc internRefcount(p: pointer): int {.exportc: "getRefcount".} =
result = 0
# this that has to equals zero, otherwise we have to round up UnitsPerPage:
when BitsPerPage mod (sizeof(int)*8) != 0:
{.error: "(BitsPerPage mod BitsPerUnit) should be zero!".}
template color(c): untyped = c.refCount and colorMask
template setColor(c, col) =
c.refcount = c.refcount and not colorMask or col
template markAsEscaped(c: PCell) =
c.refcount = c.refcount or escapedBit
template didEscape(c: PCell): bool =
(c.refCount and escapedBit) != 0
proc writeCell(file: File; msg: cstring, c: PCell) =
var kind = -1
if c.typ != nil: kind = ord(c.typ.kind)
let col = if c.color == rcGrey: 'g'
elif c.color == gch.black: 'b'
else: 'w'
when useCellIds:
let id = c.id
else:
let id = c
when defined(nimTypeNames):
c_fprintf(file, "%s %p %d escaped=%ld color=%c of type %s\n",
msg, id, kind, didEscape(c), col, c.typ.name)
elif leakDetector:
c_fprintf(file, "%s %p %d escaped=%ld color=%c from %s(%ld)\n",
msg, id, kind, didEscape(c), col, c.filename, c.line)
else:
c_fprintf(file, "%s %p %d escaped=%ld color=%c\n",
msg, id, kind, didEscape(c), col)
proc writeCell(msg: cstring, c: PCell) =
stdout.writeCell(msg, c)
proc myastToStr[T](x: T): string {.magic: "AstToStr", noSideEffect.}
template gcTrace(cell, state: untyped) =
when traceGC: writeCell(myastToStr(state), cell)
# forward declarations:
proc collectCT(gch: var GcHeap) {.benign.}
proc isOnStack(p: pointer): bool {.noinline, benign.}
proc forAllChildren(cell: PCell, op: WalkOp) {.benign.}
proc doOperation(p: pointer, op: WalkOp) {.benign.}
proc forAllChildrenAux(dest: pointer, mt: PNimType, op: WalkOp) {.benign.}
# we need the prototype here for debugging purposes
proc nimGCref(p: pointer) {.compilerproc.} =
let cell = usrToCell(p)
markAsEscaped(cell)
add(gch.additionalRoots, cell)
proc nimGCunref(p: pointer) {.compilerproc.} =
let cell = usrToCell(p)
var L = gch.additionalRoots.len-1
var i = L
let d = gch.additionalRoots.d
while i >= 0:
if d[i] == cell:
d[i] = d[L]
dec gch.additionalRoots.len
break
dec(i)
proc nimGCunrefNoCycle(p: pointer) {.compilerproc, inline.} =
discard "can we do some freeing here?"
proc nimGCunrefRC1(p: pointer) {.compilerproc, inline.} =
discard "can we do some freeing here?"
template markGrey(x: PCell) =
if x.color != 1-gch.black and gch.phase == Phase.Marking:
if not isAllocatedPtr(gch.region, x):
c_fprintf(stdout, "[GC] markGrey proc: %p\n", x)
#GC_dumpHeap()
sysAssert(false, "wtf")
x.setColor(rcGrey)
add(gch.greyStack, x)
proc asgnRef(dest: PPointer, src: pointer) {.compilerproc, inline.} =
# the code generator calls this proc!
gcAssert(not isOnStack(dest), "asgnRef")
# BUGFIX: first incRef then decRef!
if src != nil:
let s = usrToCell(src)
markAsEscaped(s)
markGrey(s)
dest[] = src
proc asgnRefNoCycle(dest: PPointer, src: pointer) {.compilerproc, inline,
deprecated: "old compiler compat".} = asgnRef(dest, src)
proc unsureAsgnRef(dest: PPointer, src: pointer) {.compilerproc.} =
# unsureAsgnRef marks 'src' as grey only if dest is not on the
# stack. It is used by the code generator if it cannot decide whether a
# reference is in the stack or not (this can happen for var parameters).
if src != nil:
let s = usrToCell(src)
markAsEscaped(s)
if not isOnStack(dest): markGrey(s)
dest[] = src
proc forAllSlotsAux(dest: pointer, n: ptr TNimNode, op: WalkOp) {.benign.} =
var d = cast[int](dest)
case n.kind
of nkSlot: forAllChildrenAux(cast[pointer](d +% n.offset), n.typ, op)
of nkList:
for i in 0..n.len-1:
forAllSlotsAux(dest, n.sons[i], op)
of nkCase:
var m = selectBranch(dest, n)
if m != nil: forAllSlotsAux(dest, m, op)
of nkNone: sysAssert(false, "forAllSlotsAux")
proc forAllChildrenAux(dest: pointer, mt: PNimType, op: WalkOp) =
var d = cast[int](dest)
if dest == nil: return # nothing to do
if ntfNoRefs notin mt.flags:
case mt.kind
of tyRef, tyString, tySequence: # leaf:
doOperation(cast[PPointer](d)[], op)
of tyObject, tyTuple:
forAllSlotsAux(dest, mt.node, op)
of tyArray, tyArrayConstr, tyOpenArray:
for i in 0..(mt.size div mt.base.size)-1:
forAllChildrenAux(cast[pointer](d +% i *% mt.base.size), mt.base, op)
else: discard
proc forAllChildren(cell: PCell, op: WalkOp) =
gcAssert(cell != nil, "forAllChildren: 1")
gcAssert(isAllocatedPtr(gch.region, cell), "forAllChildren: 2")
gcAssert(cell.typ != nil, "forAllChildren: 3")
gcAssert cell.typ.kind in {tyRef, tySequence, tyString}, "forAllChildren: 4"
let marker = cell.typ.marker
if marker != nil:
marker(cellToUsr(cell), op.int)
else:
case cell.typ.kind
of tyRef: # common case
forAllChildrenAux(cellToUsr(cell), cell.typ.base, op)
of tySequence:
var d = cast[int](cellToUsr(cell))
var s = cast[PGenericSeq](d)
if s != nil:
for i in 0..s.len-1:
forAllChildrenAux(cast[pointer](d +% align(GenericSeqSize, cell.typ.base.align) +% i *% cell.typ.base.size), cell.typ.base, op)
else: discard
{.push stackTrace: off, profiler:off.}
proc gcInvariant*() =
sysAssert(allocInv(gch.region), "injected")
when declared(markForDebug):
markForDebug(gch)
{.pop.}
include gc_common
proc initGC() =
when not defined(useNimRtl):
gch.red = (1-gch.black)
gch.cycleThreshold = InitialCycleThreshold
gch.stat.stackScans = 0
gch.stat.completedCollections = 0
gch.stat.maxThreshold = 0
gch.stat.maxStackSize = 0
gch.stat.maxStackCells = 0
gch.stat.cycleTableSize = 0
# init the rt
init(gch.additionalRoots)
init(gch.greyStack)
when hasThreadSupport:
init(gch.toDispose)
gch.gcThreadId = atomicInc(gHeapidGenerator) - 1
gcAssert(gch.gcThreadId >= 0, "invalid computed thread ID")
proc rawNewObj(typ: PNimType, size: int, gch: var GcHeap): pointer =
# generates a new object and sets its reference counter to 0
sysAssert(allocInv(gch.region), "rawNewObj begin")
gcAssert(typ.kind in {tyRef, tyString, tySequence}, "newObj: 1")
collectCT(gch)
var res = cast[PCell](rawAlloc(gch.region, size + sizeof(Cell)))
gcAssert((cast[int](res) and (MemAlign-1)) == 0, "newObj: 2")
# now it is buffered in the ZCT
res.typ = typ
when leakDetector and not hasThreadSupport:
if framePtr != nil and framePtr.prev != nil:
res.filename = framePtr.prev.filename
res.line = framePtr.prev.line
# refcount is zero, color is black, but mark it to be in the ZCT
res.refcount = allocColor()
sysAssert(isAllocatedPtr(gch.region, res), "newObj: 3")
when logGC: writeCell("new cell", res)
gcTrace(res, csAllocated)
when useCellIds:
inc gch.idGenerator
res.id = gch.idGenerator
result = cellToUsr(res)
sysAssert(allocInv(gch.region), "rawNewObj end")
{.pop.}
proc newObjNoInit(typ: PNimType, size: int): pointer {.compilerRtl.} =
result = rawNewObj(typ, size, gch)
when defined(memProfiler): nimProfile(size)
proc newObj(typ: PNimType, size: int): pointer {.compilerRtl.} =
result = rawNewObj(typ, size, gch)
zeroMem(result, size)
when defined(memProfiler): nimProfile(size)
proc newSeq(typ: PNimType, len: int): pointer {.compilerRtl.} =
# `newObj` already uses locks, so no need for them here.
let size = addInt(align(GenericSeqSize, typ.base.align), mulInt(len, typ.base.size))
result = newObj(typ, size)
cast[PGenericSeq](result).len = len
cast[PGenericSeq](result).reserved = len
when defined(memProfiler): nimProfile(size)
proc newObjRC1(typ: PNimType, size: int): pointer {.compilerRtl.} =
result = newObj(typ, size)
proc newSeqRC1(typ: PNimType, len: int): pointer {.compilerRtl.} =
result = newSeq(typ, len)
proc growObj(old: pointer, newsize: int, gch: var GcHeap): pointer =
collectCT(gch)
var ol = usrToCell(old)
sysAssert(ol.typ != nil, "growObj: 1")
gcAssert(ol.typ.kind in {tyString, tySequence}, "growObj: 2")
var res = cast[PCell](rawAlloc(gch.region, newsize + sizeof(Cell)))
var elemSize, elemAlign = 1
if ol.typ.kind != tyString:
elemSize = ol.typ.base.size
elemAlign = ol.typ.base.align
incTypeSize ol.typ, newsize
var oldsize = align(GenericSeqSize, elemAlign) + cast[PGenericSeq](old).len*elemSize
copyMem(res, ol, oldsize + sizeof(Cell))
zeroMem(cast[pointer](cast[int](res)+% oldsize +% sizeof(Cell)),
newsize-oldsize)
sysAssert((cast[int](res) and (MemAlign-1)) == 0, "growObj: 3")
when false:
# this is wrong since seqs can be shared via 'shallow':
when reallyDealloc: rawDealloc(gch.region, ol)
else:
zeroMem(ol, sizeof(Cell))
when useCellIds:
inc gch.idGenerator
res.id = gch.idGenerator
result = cellToUsr(res)
when defined(memProfiler): nimProfile(newsize-oldsize)
proc growObj(old: pointer, newsize: int): pointer {.rtl.} =
result = growObj(old, newsize, gch)
{.push profiler:off.}
template takeStartTime(workPackageSize) {.dirty.} =
const workPackage = workPackageSize
var debugticker = 1000
when withRealTime:
var steps = workPackage
var t0: Ticks
if gch.maxPause > 0: t0 = getticks()
template takeTime {.dirty.} =
when withRealTime: dec steps
dec debugticker
template checkTime {.dirty.} =
if debugticker <= 0:
#echo "in loop"
debugticker = 1000
when withRealTime:
if steps == 0:
steps = workPackage
if gch.maxPause > 0:
let duration = getticks() - t0
# the GC's measuring is not accurate and needs some cleanup actions
# (stack unmarking), so subtract some short amount of time in
# order to miss deadlines less often:
if duration >= gch.maxPause - 50_000:
return false
# ---------------- dump heap ----------------
template dumpHeapFile(gch: var GcHeap): File =
cast[File](gch.pDumpHeapFile)
proc debugGraph(s: PCell) =
c_fprintf(gch.dumpHeapFile, "child %p\n", s)
proc dumpRoot(gch: var GcHeap; s: PCell) =
if isAllocatedPtr(gch.region, s):
c_fprintf(gch.dumpHeapFile, "global_root %p\n", s)
else:
c_fprintf(gch.dumpHeapFile, "global_root_invalid %p\n", s)
proc GC_dumpHeap*(file: File) =
## Dumps the GCed heap's content to a file. Can be useful for
## debugging. Produces an undocumented text file format that
## can be translated into "dot" syntax via the "heapdump2dot" tool.
gch.pDumpHeapFile = file
var spaceIter: ObjectSpaceIter
when false:
var d = gch.decStack.d
for i in 0 .. gch.decStack.len-1:
if isAllocatedPtr(gch.region, d[i]):
c_fprintf(file, "onstack %p\n", d[i])
else:
c_fprintf(file, "onstack_invalid %p\n", d[i])
if gch.gcThreadId == 0:
for i in 0 .. globalMarkersLen-1: globalMarkers[i]()
for i in 0 .. threadLocalMarkersLen-1: threadLocalMarkers[i]()
while true:
let x = allObjectsAsProc(gch.region, addr spaceIter)
if spaceIter.state < 0: break
if isCell(x):
# cast to PCell is correct here:
var c = cast[PCell](x)
writeCell(file, "cell ", c)
forAllChildren(c, waDebug)
c_fprintf(file, "end\n")
gch.pDumpHeapFile = nil
proc GC_dumpHeap() =
var f: File
if open(f, "heap.txt", fmWrite):
GC_dumpHeap(f)
f.close()
else:
c_fprintf(stdout, "cannot write heap.txt")
# ---------------- cycle collector -------------------------------------------
proc freeCyclicCell(gch: var GcHeap, c: PCell) =
gcAssert(isAllocatedPtr(gch.region, c), "freeCyclicCell: freed pointer?")
prepareDealloc(c)
gcTrace(c, csCycFreed)
when logGC: writeCell("cycle collector dealloc cell", c)
when reallyDealloc:
sysAssert(allocInv(gch.region), "free cyclic cell")
rawDealloc(gch.region, c)
else:
gcAssert(c.typ != nil, "freeCyclicCell")
zeroMem(c, sizeof(Cell))
proc sweep(gch: var GcHeap): bool =
takeStartTime(100)
#echo "loop start"
let white = 1-gch.black
#c_fprintf(stdout, "black is %d\n", black)
while true:
let x = allObjectsAsProc(gch.region, addr gch.spaceIter)
if gch.spaceIter.state < 0: break
takeTime()
if isCell(x):
# cast to PCell is correct here:
var c = cast[PCell](x)
gcAssert c.color != rcGrey, "cell is still grey?"
if c.color == white: freeCyclicCell(gch, c)
# Since this is incremental, we MUST not set the object to 'white' here.
# We could set all the remaining objects to white after the 'sweep'
# completed but instead we flip the meaning of black/white to save one
# traversal over the heap!
checkTime()
# prepare for next iteration:
#echo "loop end"
gch.spaceIter = ObjectSpaceIter()
result = true
proc markRoot(gch: var GcHeap, c: PCell) {.inline.} =
if c.color == 1-gch.black:
c.setColor(rcGrey)
add(gch.greyStack, c)
proc markIncremental(gch: var GcHeap): bool =
var L = addr(gch.greyStack.len)
takeStartTime(100)
while L[] > 0:
var c = gch.greyStack.d[0]
if not isAllocatedPtr(gch.region, c):
c_fprintf(stdout, "[GC] not allocated anymore: %p\n", c)
#GC_dumpHeap()
sysAssert(false, "wtf")
#sysAssert(isAllocatedPtr(gch.region, c), "markIncremental: isAllocatedPtr")
gch.greyStack.d[0] = gch.greyStack.d[L[] - 1]
dec(L[])
takeTime()
if c.color == rcGrey:
c.setColor(gch.black)
forAllChildren(c, waMarkGrey)
elif c.color == (1-gch.black):
gcAssert false, "wtf why are there white objects in the greystack?"
checkTime()
gcAssert gch.greyStack.len == 0, "markIncremental: greystack not empty "
result = true
proc markGlobals(gch: var GcHeap) =
if gch.gcThreadId == 0:
for i in 0 .. globalMarkersLen-1: globalMarkers[i]()
for i in 0 .. threadLocalMarkersLen-1: threadLocalMarkers[i]()
proc doOperation(p: pointer, op: WalkOp) =
if p == nil: return
var c: PCell = usrToCell(p)
gcAssert(c != nil, "doOperation: 1")
# the 'case' should be faster than function pointers because of easy
# prediction:
case op
of waZctDecRef:
#if not isAllocatedPtr(gch.region, c):
# c_fprintf(stdout, "[GC] decref bug: %p", c)
gcAssert(isAllocatedPtr(gch.region, c), "decRef: waZctDecRef")
discard "use me for nimEscape?"
of waMarkGlobal:
template handleRoot =
if gch.dumpHeapFile.isNil:
markRoot(gch, c)
else:
dumpRoot(gch, c)
handleRoot()
discard allocInv(gch.region)
of waMarkGrey:
when false:
if not isAllocatedPtr(gch.region, c):
c_fprintf(stdout, "[GC] not allocated anymore: MarkGrey %p\n", c)
#GC_dumpHeap()
sysAssert(false, "wtf")
if c.color == 1-gch.black:
c.setColor(rcGrey)
add(gch.greyStack, c)
of waDebug: debugGraph(c)
proc nimGCvisit(d: pointer, op: int) {.compilerRtl.} =
doOperation(d, WalkOp(op))
proc gcMark(gch: var GcHeap, p: pointer) {.inline.} =
# the addresses are not as cells on the stack, so turn them to cells:
sysAssert(allocInv(gch.region), "gcMark begin")
var cell = usrToCell(p)
var c = cast[int](cell)
if c >% PageSize:
# fast check: does it look like a cell?
var objStart = cast[PCell](interiorAllocatedPtr(gch.region, cell))
if objStart != nil:
# mark the cell:
markRoot(gch, objStart)
sysAssert(allocInv(gch.region), "gcMark end")
proc markStackAndRegisters(gch: var GcHeap) {.noinline, cdecl.} =
forEachStackSlot(gch, gcMark)
proc collectALittle(gch: var GcHeap): bool =
case gch.phase
of Phase.None:
if getOccupiedMem(gch.region) >= gch.cycleThreshold:
gch.phase = Phase.Marking
markGlobals(gch)
result = collectALittle(gch)
#when false: c_fprintf(stdout, "collectALittle: introduced bug E %ld\n", gch.phase)
#discard allocInv(gch.region)
of Phase.Marking:
when hasThreadSupport:
for c in gch.toDispose:
nimGCunref(c)
prepareForInteriorPointerChecking(gch.region)
markStackAndRegisters(gch)
inc(gch.stat.stackScans)
if markIncremental(gch):
gch.phase = Phase.Sweeping
gch.red = 1 - gch.red
of Phase.Sweeping:
gcAssert gch.greyStack.len == 0, "greystack not empty"
when hasThreadSupport:
for c in gch.toDispose:
nimGCunref(c)
if sweep(gch):
gch.phase = Phase.None
# flip black/white meanings:
gch.black = 1 - gch.black
gcAssert gch.red == 1 - gch.black, "red color is wrong"
inc(gch.stat.completedCollections)
result = true
proc collectCTBody(gch: var GcHeap) =
when withRealTime:
let t0 = getticks()
sysAssert(allocInv(gch.region), "collectCT: begin")
when not nimCoroutines:
gch.stat.maxStackSize = max(gch.stat.maxStackSize, stackSize())
#gch.stat.maxStackCells = max(gch.stat.maxStackCells, gch.decStack.len)
if collectALittle(gch):
gch.cycleThreshold = max(InitialCycleThreshold, getOccupiedMem() *
CycleIncrease)
gch.stat.maxThreshold = max(gch.stat.maxThreshold, gch.cycleThreshold)
sysAssert(allocInv(gch.region), "collectCT: end")
when withRealTime:
let duration = getticks() - t0
gch.stat.maxPause = max(gch.stat.maxPause, duration)
when defined(reportMissedDeadlines):
if gch.maxPause > 0 and duration > gch.maxPause:
c_fprintf(stdout, "[GC] missed deadline: %ld\n", duration)
when nimCoroutines:
proc currentStackSizes(): int =
for stack in items(gch.stack):
result = result + stack.stackSize()
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.
when nimCoroutines:
let stackMarkCosts = max(currentStackSizes() div (16*sizeof(int)), ZctThreshold)
else:
let stackMarkCosts = max(stackSize() div (16*sizeof(int)), ZctThreshold)
if (gch.greyStack.len >= stackMarkCosts or (cycleGC and
getOccupiedMem(gch.region)>=gch.cycleThreshold) or alwaysGC) and
gch.recGcLock == 0:
collectCTBody(gch)
when withRealTime:
proc toNano(x: int): Nanos {.inline.} =
result = x * 1000
proc GC_setMaxPause*(MaxPauseInUs: int) =
gch.maxPause = MaxPauseInUs.toNano
proc GC_step(gch: var GcHeap, us: int, strongAdvice: bool) =
gch.maxPause = us.toNano
#if (getOccupiedMem(gch.region)>=gch.cycleThreshold) or
# alwaysGC or strongAdvice:
collectCTBody(gch)
proc GC_step*(us: int, strongAdvice = false, stackSize = -1) {.noinline.} =
if stackSize >= 0:
var stackTop {.volatile.}: pointer
gch.getActiveStack().pos = addr(stackTop)
for stack in gch.stack.items():
stack.bottomSaved = stack.bottom
when stackIncreases:
stack.bottom = cast[pointer](
cast[int](stack.pos) - sizeof(pointer) * 6 - stackSize)
else:
stack.bottom = cast[pointer](
cast[int](stack.pos) + sizeof(pointer) * 6 + stackSize)
GC_step(gch, us, strongAdvice)
if stackSize >= 0:
for stack in gch.stack.items():
stack.bottom = stack.bottomSaved
when not defined(useNimRtl):
proc GC_disable() =
inc(gch.recGcLock)
proc GC_enable() =
if gch.recGcLock > 0:
dec(gch.recGcLock)
proc GC_setStrategy(strategy: GC_Strategy) =
discard
proc GC_enableMarkAndSweep() = discard
proc GC_disableMarkAndSweep() = discard
proc GC_fullCollect() =
var oldThreshold = gch.cycleThreshold
gch.cycleThreshold = 0 # forces cycle collection
collectCT(gch)
gch.cycleThreshold = oldThreshold
proc GC_getStatistics(): string =
GC_disable()
result = "[GC] total memory: " & $(getTotalMem()) & "\n" &
"[GC] occupied memory: " & $(getOccupiedMem()) & "\n" &
"[GC] stack scans: " & $gch.stat.stackScans & "\n" &
"[GC] stack cells: " & $gch.stat.maxStackCells & "\n" &
"[GC] completed collections: " & $gch.stat.completedCollections & "\n" &
"[GC] max threshold: " & $gch.stat.maxThreshold & "\n" &
"[GC] grey stack capacity: " & $gch.greyStack.cap & "\n" &
"[GC] max cycle table size: " & $gch.stat.cycleTableSize & "\n" &
"[GC] max pause time [ms]: " & $(gch.stat.maxPause div 1000_000) & "\n"
when nimCoroutines:
result.add "[GC] number of stacks: " & $gch.stack.len & "\n"
for stack in items(gch.stack):
result.add "[GC] stack " & stack.bottom.repr & "[GC] max stack size " & $stack.maxStackSize & "\n"
else:
result.add "[GC] max stack size: " & $gch.stat.maxStackSize & "\n"
GC_enable()
{.pop.}