diff --git a/src/runtime/mgc.go b/src/runtime/mgc.go
index 430b7aa657a..58b52e8bed4 100644
--- a/src/runtime/mgc.go
+++ b/src/runtime/mgc.go
@@ -1497,8 +1497,10 @@ func gcBgMarkWorker(_p_ *p) {
 				throw("gcBgMarkWorker: unexpected gcMarkWorkerMode")
 			case gcMarkWorkerDedicatedMode:
 				gcDrain(&_p_.gcw, gcDrainNoBlock|gcDrainFlushBgCredit)
-			case gcMarkWorkerFractionalMode, gcMarkWorkerIdleMode:
+			case gcMarkWorkerFractionalMode:
 				gcDrain(&_p_.gcw, gcDrainUntilPreempt|gcDrainFlushBgCredit)
+			case gcMarkWorkerIdleMode:
+				gcDrain(&_p_.gcw, gcDrainIdle|gcDrainUntilPreempt|gcDrainFlushBgCredit)
 			}
 			casgstatus(gp, _Gwaiting, _Grunning)
 		})
diff --git a/src/runtime/mgcmark.go b/src/runtime/mgcmark.go
index cfd24e06fb6..85130bf2279 100644
--- a/src/runtime/mgcmark.go
+++ b/src/runtime/mgcmark.go
@@ -33,6 +33,14 @@ const (
 	// This must be > _MaxSmallSize so that the object base is the
 	// span base.
 	maxObletBytes = 128 << 10
+
+	// idleCheckThreshold specifies how many units of work to do
+	// between run queue checks in an idle worker. Assuming a scan
+	// rate of 1 MB/ms, this is ~100 µs. Lower values have higher
+	// overhead in the scan loop (the scheduler check may perform
+	// a syscall, so its overhead is nontrivial). Higher values
+	// make the system less responsive to incoming work.
+	idleCheckThreshold = 100000
 )
 
 // gcMarkRootPrepare queues root scanning jobs (stacks, globals, and
@@ -991,6 +999,7 @@ const (
 	gcDrainUntilPreempt gcDrainFlags = 1 << iota
 	gcDrainNoBlock
 	gcDrainFlushBgCredit
+	gcDrainIdle
 
 	// gcDrainBlock means neither gcDrainUntilPreempt or
 	// gcDrainNoBlock. It is the default, but callers should use
@@ -1004,6 +1013,9 @@ const (
 // If flags&gcDrainUntilPreempt != 0, gcDrain returns when g.preempt
 // is set. This implies gcDrainNoBlock.
 //
+// If flags&gcDrainIdle != 0, gcDrain returns when there is other work
+// to do. This implies gcDrainNoBlock.
+//
 // If flags&gcDrainNoBlock != 0, gcDrain returns as soon as it is
 // unable to get more work. Otherwise, it will block until all
 // blocking calls are blocked in gcDrain.
@@ -1020,8 +1032,14 @@ func gcDrain(gcw *gcWork, flags gcDrainFlags) {
 
 	gp := getg().m.curg
 	preemptible := flags&gcDrainUntilPreempt != 0
-	blocking := flags&(gcDrainUntilPreempt|gcDrainNoBlock) == 0
+	blocking := flags&(gcDrainUntilPreempt|gcDrainIdle|gcDrainNoBlock) == 0
 	flushBgCredit := flags&gcDrainFlushBgCredit != 0
+	idle := flags&gcDrainIdle != 0
+
+	initScanWork := gcw.scanWork
+	// idleCheck is the scan work at which to perform the next
+	// idle check with the scheduler.
+	idleCheck := initScanWork + idleCheckThreshold
 
 	// Drain root marking jobs.
 	if work.markrootNext < work.markrootJobs {
@@ -1031,11 +1049,12 @@ func gcDrain(gcw *gcWork, flags gcDrainFlags) {
 				break
 			}
 			markroot(gcw, job)
+			if idle && pollWork() {
+				goto done
+			}
 		}
 	}
 
-	initScanWork := gcw.scanWork
-
 	// Drain heap marking jobs.
 	for !(preemptible && gp.preempt) {
 		// Try to keep work available on the global queue. We used to
@@ -1071,7 +1090,15 @@ func gcDrain(gcw *gcWork, flags gcDrainFlags) {
 				gcFlushBgCredit(gcw.scanWork - initScanWork)
 				initScanWork = 0
 			}
+			idleCheck -= gcw.scanWork
 			gcw.scanWork = 0
+
+			if idle && idleCheck <= 0 {
+				idleCheck += idleCheckThreshold
+				if pollWork() {
+					break
+				}
+			}
 		}
 	}
 
@@ -1079,6 +1106,7 @@ func gcDrain(gcw *gcWork, flags gcDrainFlags) {
 	// point because we must preserve the condition that the work
 	// buffers are empty.
 
+done:
 	// Flush remaining scan work credit.
 	if gcw.scanWork > 0 {
 		atomic.Xaddint64(&gcController.scanWork, gcw.scanWork)
diff --git a/src/runtime/proc.go b/src/runtime/proc.go
index 90e6d18ee21..1b21b37de83 100644
--- a/src/runtime/proc.go
+++ b/src/runtime/proc.go
@@ -2053,6 +2053,27 @@ stop:
 	goto top
 }
 
+// pollWork returns true if there is non-background work this P could
+// be doing. This is a fairly lightweight check to be used for
+// background work loops, like idle GC. It checks a subset of the
+// conditions checked by the actual scheduler.
+func pollWork() bool {
+	if sched.runqsize != 0 {
+		return true
+	}
+	p := getg().m.p.ptr()
+	if !runqempty(p) {
+		return true
+	}
+	if netpollinited() && sched.lastpoll != 0 {
+		if gp := netpoll(false); gp != nil {
+			injectglist(gp)
+			return true
+		}
+	}
+	return false
+}
+
 func resetspinning() {
 	_g_ := getg()
 	if !_g_.m.spinning {