Sweep pages with lowest live memory first.

src/spaces.cc

Index: src/spaces.cc
diff --git a/src/spaces.cc b/src/spaces.cc
index 701d46f38bc63473e56cc367caddabfc210f8657..b0c7241cc39e771fefd826dd53f88767cdd9dfb8 100644
--- a/src/spaces.cc
+++ b/src/spaces.cc
@@ -2503,14 +2503,39 @@ bool LargeObjectSpace::ReserveSpace(int bytes) {
 }
 
 
+intptr_t PagedSpace::SweepPageWithLowestLiveMemory() {
+  Page* p = first_unswept_page_;
+  Page* sweep_canditate = NULL;
+
+  while (p != anchor()) {
+    if (ShouldBeSweptLazily(p) && !p->WasSweptConservatively()) {
+      if (sweep_canditate == NULL ||
+          p->LiveBytes() < sweep_canditate->LiveBytes()) {
+        sweep_canditate = p;
+      }
+    }
+    p = p->next_page();
+  }
+
+  if (sweep_canditate != NULL) {
+    DecreaseUnsweptFreeBytes(sweep_canditate);
+    return MarkCompactCollector::
+        SweepConservatively<MarkCompactCollector::SWEEP_SEQUENTIALLY>(
+            this, NULL, sweep_canditate);
+  }
+  return 0;
+}
+
+
 bool PagedSpace::AdvanceSweeper(intptr_t bytes_to_sweep) {
   if (IsLazySweepingComplete()) return true;
 
-  intptr_t freed_bytes = 0;
+  intptr_t freed_bytes = SweepPageWithLowestLiveMemory();
+
   Page* p = first_unswept_page_;
-  do {
+  while (freed_bytes < bytes_to_sweep && p != anchor()) {
     Page* next_page = p->next_page();
-    if (ShouldBeSweptLazily(p)) {
+    if (ShouldBeSweptLazily(p) && !p->WasSweptConservatively()) {
       if (FLAG_gc_verbose) {
         PrintF("Sweeping 0x%" V8PRIxPTR " lazily advanced.\n",
                reinterpret_cast<intptr_t>(p));
@@ -2522,7 +2547,7 @@ bool PagedSpace::AdvanceSweeper(intptr_t bytes_to_sweep) {
                   this, NULL, p);
     }
     p = next_page;
-  } while (p != anchor() && freed_bytes < bytes_to_sweep);
+  }
 
   if (p == anchor()) {
     first_unswept_page_ = Page::FromAddress(NULL);