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

			// mark using checkmark bits, to check that we
			// didn't forget to mark anything during the
			// concurrent mark process.
			startCheckmarks()
			gcResetMarkState()
			gcw := &getg().m.p.ptr().gcw
			gcDrain(gcw, 0)
			wbBufFlush1(getg().m.p.ptr())
			gcw.dispose()
			endCheckmarks()
		}

		// marking is complete so we can turn the write barrier off
		setGCPhase(_GCoff)
		stwSwept = gcSweep(work.mode)