[heap] Adjust upper limit in ComputeMaxSemiSpaceSize.

This ensures that 2GB devices get 512K initial semi-space.

Bug: chromium:735649
TBR: mlippautz@chromium.org
Change-Id: I864c9dfa7cd3ea9040fa56d81d6bf1187c1cf776
Reviewed-on: https://chromium-review.googlesource.com/608129Reviewed-by: Ulan Degenbaev <ulan@chromium.org>
Commit-Queue: Ulan Degenbaev <ulan@chromium.org>
Cr-Commit-Position: refs/heads/master@{#47246}

src/heap/heap.h

@@ -1306,7 +1306,7 @@ class Heap {
 
   static size_t ComputeMaxSemiSpaceSize(uint64_t physical_memory) {
     const uint64_t min_physical_memory = 512 * MB;
-    const uint64_t max_physical_memory = 2 * static_cast<uint64_t>(GB);
+    const uint64_t max_physical_memory = 3 * static_cast<uint64_t>(GB);
 
     uint64_t capped_physical_memory =
         Max(Min(physical_memory, max_physical_memory), min_physical_memory);

test/unittests/heap/heap-unittest.cc

@@ -68,8 +68,8 @@ TEST(Heap, SemiSpaceSize) {
   const size_t pm = i::Heap::kPointerMultiplier;
   ASSERT_EQ(1u * pm * MB / 2, i::Heap::ComputeMaxSemiSpaceSize(0u) * KB);
   ASSERT_EQ(1u * pm * MB / 2, i::Heap::ComputeMaxSemiSpaceSize(512u * MB) * KB);
-  ASSERT_EQ(3u * pm * MB, i::Heap::ComputeMaxSemiSpaceSize(1024u * MB) * KB);
-  ASSERT_EQ(8u * pm * MB, i::Heap::ComputeMaxSemiSpaceSize(2024u * MB) * KB);
+  ASSERT_EQ(2u * pm * MB, i::Heap::ComputeMaxSemiSpaceSize(1024u * MB) * KB);
+  ASSERT_EQ(5u * pm * MB, i::Heap::ComputeMaxSemiSpaceSize(2024u * MB) * KB);
   ASSERT_EQ(8u * pm * MB, i::Heap::ComputeMaxSemiSpaceSize(4095u * MB) * KB);
 }