Follow up on CL 122665.

We now do the two-step memory protection strategy (first protect the
from space with PROT_READ and later protect it with PROT_NONE) only if
the from space is a rosalloc space (excluding the more common bump
pointer space case). This strengthens the GC verification for the bump
pointer space case as we avoid the case where mutators run while the
from space is PROT_READ rather than PROT_NONE.

Add a command line flag to override the minimum interval for the
hspace compaction for OOM and set it to zero in the gcstress/gcverify
run-tests to run the hspace compaction more frequently in tests.

Fix some comments.

Bug: 18960494
Change-Id: I518b011e026f578e53c4ec269cfb82865b0fae68

2 files changed, 19 insertions, 7 deletions

diff --git a/runtime/gc/collector/semi_space.cc b/runtime/gc/collector/semi_space.cc
index 681bfaa..82d6992 100644
--- a/runtime/gc/collector/semi_space.cc
+++ b/runtime/gc/collector/semi_space.cc
@@ -251,13 +251,19 @@ void SemiSpace::MarkingPhase() {
   // Note: Freed bytes can be negative if we copy form a compacted space to a free-list backed
   // space.
   RecordFree(ObjectBytePair(from_objects - to_objects, from_bytes - to_bytes));
-  // Clear the from space. Protect it with PROT_READ here and if
-  // kProtectFromSpace is true, will protect it with PROT_NONE later
-  // in FinishPhase() so the rosalloc verification works (can read the
-  // metadata magic number.)
+  // Clear and protect the from space.
   from_space_->Clear();
-  VLOG(heap) << "Protecting from_space_ with PROT_READ : " << *from_space_;
-  from_space_->GetMemMap()->Protect(PROT_READ);
+  if (kProtectFromSpace && !from_space_->IsRosAllocSpace()) {
+    // Protect with PROT_NONE.
+    VLOG(heap) << "Protecting from_space_ : " << *from_space_;
+    from_space_->GetMemMap()->Protect(PROT_NONE);
+  } else {
+    // If RosAllocSpace, we'll leave it as PROT_READ here so the
+    // rosaloc verification can read the metadata magic number and
+    // protect it with PROT_NONE later in FinishPhase().
+    VLOG(heap) << "Protecting from_space_ with PROT_READ : " << *from_space_;
+    from_space_->GetMemMap()->Protect(PROT_READ);
+  }
   heap_->PreSweepingGcVerification(this);
   if (swap_semi_spaces_) {
     heap_->SwapSemiSpaces();
@@ -752,7 +758,7 @@ void SemiSpace::SetFromSpace(space::ContinuousMemMapAllocSpace* from_space) {
 
 void SemiSpace::FinishPhase() {
   TimingLogger::ScopedTiming t(__FUNCTION__, GetTimings());
-  if (kProtectFromSpace) {
+  if (kProtectFromSpace && from_space_->IsRosAllocSpace()) {
     VLOG(heap) << "Protecting from_space_ with PROT_NONE : " << *from_space_;
     from_space_->GetMemMap()->Protect(PROT_NONE);
   }
diff --git a/runtime/parsed_options.cc b/runtime/parsed_options.cc
index 4ba3cb9..efc4a71 100644
--- a/runtime/parsed_options.cc
+++ b/runtime/parsed_options.cc
@@ -413,6 +413,12 @@ bool ParsedOptions::Parse(const RuntimeOptions& options, bool ignore_unrecognize
       use_homogeneous_space_compaction_for_oom_ = true;
     } else if (option == "-XX:DisableHSpaceCompactForOOM") {
       use_homogeneous_space_compaction_for_oom_ = false;
+    } else if (StartsWith(option, "-XX:HspaceCompactForOOMMinIntervalMs=")) {
+      unsigned int value;
+      if (!ParseUnsignedInteger(option, '=', &value)) {
+        return false;
+      }
+      min_interval_homogeneous_space_compaction_by_oom_ = MsToNs(value);
     } else if (StartsWith(option, "-D")) {
       properties_.push_back(option.substr(strlen("-D")));
     } else if (StartsWith(option, "-Xjnitrace:")) {