Improve CC handling for immune objects
Currently we reduce ram for immune objects by racing agianst the
mutators to try and finish processing them before the mutators
change many objects to gray. However there is still a window of time
where the mutator can dirty immune pages by changing the lock words
to gray. These pages remain dirty for the lifetime of the app.
This CL changes uses the FlipCallback pause to gray all of the
immune objects that have a dirty card. Once these objects are all
gray we don't to gray any more objects in the immune spaces since
these objects are the only ones that may reference non immune
objects.
Also only scan objects that are gray when scanning immune spaces to
reduce scanning time.
System wide PSS after boot on N9, before:
61668 kB: .art mmap
11249 kB: .Zygote
After:
36013 kB: .art mmap
12251 kB: .Zygote
Results are better than demonstrated since there are more apps
running after.
Maps PSS / Private Dirty, before:
.art mmap 3703 3116
.Zygote 577 480
After:
.art mmap 1655 1092
.Zygote 476 392
System server before:
.art mmap 4453 3956
.Zygote 849 780
After:
.art mmap 2326 1748
.Zygote 640 564
EAAC:
Before:
ScanImmuneSpaces takes 669.434ms GC time
Scores: 718, 761, 753 average 744
GC time: 4.2s, 4.35s, 4.3s average 4.28s
After:
ScanImmuneSpaces takes 138.328ms GC time
Scores: 731, 730, 704 average 722
GC time: 3.92s, 3.83s, 3.85s average 3.87s
Additional GC pause time is 285us on Maps on N9.
TODO: Reduce this pause time.
Test: N9 booting, test-art-host, EAAC all run with CC
Bug: 29516968
Bug: 12687968
Change-Id: I584b10d017547b321f33eb23fb5d64372af6f69c
diff --git a/runtime/gc/accounting/mod_union_table.h b/runtime/gc/accounting/mod_union_table.h
index a7a4246..bf665c5 100644
--- a/runtime/gc/accounting/mod_union_table.h
+++ b/runtime/gc/accounting/mod_union_table.h
@@ -68,6 +68,9 @@
// spaces which are stored in the mod-union table.
virtual void UpdateAndMarkReferences(MarkObjectVisitor* visitor) = 0;
+ // Visit all of the objects that may contain references to other spaces.
+ virtual void VisitObjects(ObjectCallback* callback, void* arg) = 0;
+
// Verification, sanity checks that we don't have clean cards which conflict with out cached data
// for said cards. Exclusive lock is required since verify sometimes uses
// SpaceBitmap::VisitMarkedRange and VisitMarkedRange can't know if the callback will modify the
@@ -78,6 +81,9 @@
// doesn't need to be aligned.
virtual bool ContainsCardFor(uintptr_t addr) = 0;
+ // Filter out cards that don't need to be marked. Automatically done with UpdateAndMarkReferences.
+ void FilterCards();
+
virtual void Dump(std::ostream& os) = 0;
space::ContinuousSpace* GetSpace() {
@@ -115,6 +121,10 @@
SHARED_REQUIRES(Locks::mutator_lock_)
REQUIRES(Locks::heap_bitmap_lock_);
+ virtual void VisitObjects(ObjectCallback* callback, void* arg) OVERRIDE
+ REQUIRES(Locks::heap_bitmap_lock_)
+ SHARED_REQUIRES(Locks::mutator_lock_);
+
// Exclusive lock is required since verify uses SpaceBitmap::VisitMarkedRange and
// VisitMarkedRange can't know if the callback will modify the bitmap or not.
void Verify() OVERRIDE
@@ -156,6 +166,10 @@
REQUIRES(Locks::heap_bitmap_lock_)
SHARED_REQUIRES(Locks::mutator_lock_);
+ virtual void VisitObjects(ObjectCallback* callback, void* arg) OVERRIDE
+ REQUIRES(Locks::heap_bitmap_lock_)
+ SHARED_REQUIRES(Locks::mutator_lock_);
+
// Nothing to verify.
virtual void Verify() OVERRIDE {}