package runtime
import (
+ "internal/abi"
"internal/goarch"
+ "internal/goexperiment"
"runtime/internal/atomic"
"runtime/internal/sys"
"unsafe"
userG := getg().m.curg
selfScan := gp == userG && readgstatus(userG) == _Grunning
if selfScan {
- casgstatus(userG, _Grunning, _Gwaiting)
- userG.waitreason = waitReasonGarbageCollectionScan
+ casGToWaiting(userG, _Grunning, waitReasonGarbageCollectionScan)
}
// TODO: suspendG blocks (and spins) until gp
// Mark everything that can be reached from
// the object (but *not* the object itself or
// we'll never collect it).
- scanobject(p, gcw)
+ if !s.spanclass.noscan() {
+ scanobject(p, gcw)
+ }
// The special itself is a root.
scanblock(uintptr(unsafe.Pointer(&spf.fn)), goarch.PtrSize, &oneptrmask[0], gcw, nil)
traced := false
retry:
- if go119MemoryLimitSupport && gcCPULimiter.limiting() {
+ if gcCPULimiter.limiting() {
// If the CPU limiter is enabled, intentionally don't
// assist to reduce the amount of CPU time spent in the GC.
if traced {
- traceGCMarkAssistDone()
+ trace := traceAcquire()
+ if trace.ok() {
+ trace.GCMarkAssistDone()
+ traceRelease(trace)
+ }
}
return
}
// We were able to steal all of the credit we
// needed.
if traced {
- traceGCMarkAssistDone()
+ trace := traceAcquire()
+ if trace.ok() {
+ trace.GCMarkAssistDone()
+ traceRelease(trace)
+ }
}
return
}
}
-
- if trace.enabled && !traced {
- traced = true
- traceGCMarkAssistStart()
+ if traceEnabled() && !traced {
+ trace := traceAcquire()
+ if trace.ok() {
+ traced = true
+ trace.GCMarkAssistStart()
+ traceRelease(trace)
+ }
}
// Perform assist work
// this G's assist debt, or the GC cycle is over.
}
if traced {
- traceGCMarkAssistDone()
+ trace := traceAcquire()
+ if trace.ok() {
+ trace.GCMarkAssistDone()
+ traceRelease(trace)
+ }
}
}
// The gcBlackenEnabled check in malloc races with the
// store that clears it but an atomic check in every malloc
// would be a performance hit.
- // Instead we recheck it here on the non-preemptable system
+ // Instead we recheck it here on the non-preemptible system
// stack to determine if we should perform an assist.
// GC is done, so ignore any remaining debt.
}
// gcDrainN requires the caller to be preemptible.
- casgstatus(gp, _Grunning, _Gwaiting)
- gp.waitreason = waitReasonGCAssistMarking
+ casGToWaiting(gp, _Grunning, waitReasonGCAssistMarking)
// drain own cached work first in the hopes that it
// will be more cache friendly.
return false
}
// Park.
- goparkunlock(&work.assistQueue.lock, waitReasonGCAssistWait, traceEvGoBlockGC, 2)
+ goparkunlock(&work.assistQueue.lock, waitReasonGCAssistWait, traceBlockGCMarkAssist, 2)
return true
}
}
// Scan the stack. Accumulate a list of stack objects.
- scanframe := func(frame *stkframe, unused unsafe.Pointer) bool {
- scanframeworker(frame, &state, gcw)
- return true
+ var u unwinder
+ for u.init(gp, 0); u.valid(); u.next() {
+ scanframeworker(&u.frame, &state, gcw)
}
- gentraceback(^uintptr(0), ^uintptr(0), 0, gp, 0, nil, 0x7fffffff, scanframe, nil, 0)
// Find additional pointers that point into the stack from the heap.
// Currently this includes defers and panics. See also function copystack.
print("scanframe ", funcname(frame.fn), "\n")
}
- isAsyncPreempt := frame.fn.valid() && frame.fn.funcID == funcID_asyncPreempt
- isDebugCall := frame.fn.valid() && frame.fn.funcID == funcID_debugCallV2
+ isAsyncPreempt := frame.fn.valid() && frame.fn.funcID == abi.FuncID_asyncPreempt
+ isDebugCall := frame.fn.valid() && frame.fn.funcID == abi.FuncID_debugCallV2
if state.conservative || isAsyncPreempt || isDebugCall {
if debugScanConservative {
println("conservatively scanning function", funcname(frame.fn), "at PC", hex(frame.continpc))
}
// Scan arguments to this frame.
- if frame.arglen != 0 {
+ if n := frame.argBytes(); n != 0 {
// TODO: We could pass the entry argument map
// to narrow this down further.
- scanConservative(frame.argp, frame.arglen, nil, gcw, state)
+ scanConservative(frame.argp, n, nil, gcw, state)
}
if isAsyncPreempt || isDebugCall {
return
}
- locals, args, objs := getStackMap(frame, &state.cache, false)
+ locals, args, objs := frame.getStackMap(false)
// Scan local variables if stack frame has been allocated.
if locals.n > 0 {
gcDrainFractional
)
+// gcDrainMarkWorkerIdle is a wrapper for gcDrain that exists to better account
+// mark time in profiles.
+func gcDrainMarkWorkerIdle(gcw *gcWork) {
+ gcDrain(gcw, gcDrainIdle|gcDrainUntilPreempt|gcDrainFlushBgCredit)
+}
+
+// gcDrainMarkWorkerDedicated is a wrapper for gcDrain that exists to better account
+// mark time in profiles.
+func gcDrainMarkWorkerDedicated(gcw *gcWork, untilPreempt bool) {
+ flags := gcDrainFlushBgCredit
+ if untilPreempt {
+ flags |= gcDrainUntilPreempt
+ }
+ gcDrain(gcw, flags)
+}
+
+// gcDrainMarkWorkerFractional is a wrapper for gcDrain that exists to better account
+// mark time in profiles.
+func gcDrainMarkWorkerFractional(gcw *gcWork) {
+ gcDrain(gcw, gcDrainFractional|gcDrainUntilPreempt|gcDrainFlushBgCredit)
+}
+
// gcDrain scans roots and objects in work buffers, blackening grey
// objects until it is unable to get more work. It may return before
// GC is done; it's the caller's responsibility to balance work from
// credit to gcController.bgScanCredit every gcCreditSlack units of
// scan work.
//
-// gcDrain will always return if there is a pending STW.
+// gcDrain will always return if there is a pending STW or forEachP.
+//
+// Disabling write barriers is necessary to ensure that after we've
+// confirmed that we've drained gcw, that we don't accidentally end
+// up flipping that condition by immediately adding work in the form
+// of a write barrier buffer flush.
+//
+// Don't set nowritebarrierrec because it's safe for some callees to
+// have write barriers enabled.
//
//go:nowritebarrier
func gcDrain(gcw *gcWork, flags gcDrainFlags) {
- if !writeBarrier.needed {
+ if !writeBarrier.enabled {
throw("gcDrain phase incorrect")
}
+ // N.B. We must be running in a non-preemptible context, so it's
+ // safe to hold a reference to our P here.
gp := getg().m.curg
+ pp := gp.m.p.ptr()
preemptible := flags&gcDrainUntilPreempt != 0
flushBgCredit := flags&gcDrainFlushBgCredit != 0
idle := flags&gcDrainIdle != 0
// Drain root marking jobs.
if work.markrootNext < work.markrootJobs {
- // Stop if we're preemptible or if someone wants to STW.
- for !(gp.preempt && (preemptible || atomic.Load(&sched.gcwaiting) != 0)) {
+ // Stop if we're preemptible, if someone wants to STW, or if
+ // someone is calling forEachP.
+ for !(gp.preempt && (preemptible || sched.gcwaiting.Load() || pp.runSafePointFn != 0)) {
job := atomic.Xadd(&work.markrootNext, +1) - 1
if job >= work.markrootJobs {
break
}
// Drain heap marking jobs.
- // Stop if we're preemptible or if someone wants to STW.
- for !(gp.preempt && (preemptible || atomic.Load(&sched.gcwaiting) != 0)) {
+ //
+ // Stop if we're preemptible, if someone wants to STW, or if
+ // someone is calling forEachP.
+ //
+ // TODO(mknyszek): Consider always checking gp.preempt instead
+ // of having the preempt flag, and making an exception for certain
+ // mark workers in retake. That might be simpler than trying to
+ // enumerate all the reasons why we might want to preempt, even
+ // if we're supposed to be mostly non-preemptible.
+ for !(gp.preempt && (preemptible || sched.gcwaiting.Load() || pp.runSafePointFn != 0)) {
// Try to keep work available on the global queue. We used to
// check if there were waiting workers, but it's better to
// just keep work available than to make workers wait. In the
// Flush the write barrier
// buffer; this may create
// more work.
- wbBufFlush(nil, 0)
+ wbBufFlush()
b = gcw.tryGet()
}
}
//go:nowritebarrier
//go:systemstack
func gcDrainN(gcw *gcWork, scanWork int64) int64 {
- if !writeBarrier.needed {
+ if !writeBarrier.enabled {
throw("gcDrainN phase incorrect")
}
if b == 0 {
// Flush the write barrier buffer;
// this may create more work.
- wbBufFlush(nil, 0)
+ wbBufFlush()
b = gcw.tryGet()
}
}
if n == 0 {
throw("scanobject n == 0")
}
+ if s.spanclass.noscan() {
+ // Correctness-wise this is ok, but it's inefficient
+ // if noscan objects reach here.
+ throw("scanobject of a noscan object")
+ }
+ var tp typePointers
if n > maxObletBytes {
// Large object. Break into oblets for better
// parallelism and lower latency.
if b == s.base() {
- // It's possible this is a noscan object (not
- // from greyobject, but from other code
- // paths), in which case we must *not* enqueue
- // oblets since their bitmaps will be
- // uninitialized.
- if s.spanclass.noscan() {
- // Bypass the whole scan.
- gcw.bytesMarked += uint64(n)
- return
- }
-
// Enqueue the other oblets to scan later.
// Some oblets may be in b's scalar tail, but
// these will be marked as "no more pointers",
// must be a large object, s.base() is the beginning
// of the object.
n = s.base() + s.elemsize - b
- if n > maxObletBytes {
- n = maxObletBytes
+ n = min(n, maxObletBytes)
+ if goexperiment.AllocHeaders {
+ tp = s.typePointersOfUnchecked(s.base())
+ tp = tp.fastForward(b-tp.addr, b+n)
+ }
+ } else {
+ if goexperiment.AllocHeaders {
+ tp = s.typePointersOfUnchecked(b)
}
}
- hbits := heapBitsForAddr(b, n)
+ var hbits heapBits
+ if !goexperiment.AllocHeaders {
+ hbits = heapBitsForAddr(b, n)
+ }
var scanSize uintptr
for {
var addr uintptr
- if hbits, addr = hbits.nextFast(); addr == 0 {
- if hbits, addr = hbits.next(); addr == 0 {
- break
+ if goexperiment.AllocHeaders {
+ if tp, addr = tp.nextFast(); addr == 0 {
+ if tp, addr = tp.next(b + n); addr == 0 {
+ break
+ }
+ }
+ } else {
+ if hbits, addr = hbits.nextFast(); addr == 0 {
+ if hbits, addr = hbits.next(); addr == 0 {
+ break
+ }
}
}
//
//go:nowritebarrier
//go:nosplit
-func gcmarknewobject(span *mspan, obj, size, scanSize uintptr) {
+func gcmarknewobject(span *mspan, obj, size uintptr) {
if useCheckmark { // The world should be stopped so this should not happen.
throw("gcmarknewobject called while doing checkmark")
}