@@ -747,7 +747,7 @@ final class Arm64VMOffsets extends VMOffsets {
   @override
   int get Page_kBytesPerCardLog2 => 0x8;
   @override
-  int get Page_kPageMask => -0x80000;
+  int get Page_kPageMask => -0x200000;
   @override
   int get Record_kMaxElements => 0xffff;
   @override
@@ -1824,7 +1824,7 @@ final class Arm64ProductVMOffsets extends VMOffsets {
   @override
   int get Page_kBytesPerCardLog2 => 0x8;
   @override
-  int get Page_kPageMask => -0x80000;
+  int get Page_kPageMask => -0x200000;
   @override
   int get Record_kMaxElements => 0xffff;
   @override
 
@@ -1,7 +1,8 @@
 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
-// VMOptions=--new_gen_semi_max_size=1 --no_inline_alloc
+
+// VMOptions=--new_gen_semi_max_size=2 --no_inline_alloc
 
 // Regression test for slow-path allocation in the allocation stub.
 
 
@@ -1,8 +1,8 @@
 // Copyright (c) 2022, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
-//
-// VMOptions=--new_gen_semi_max_size=1
+
+// VMOptions=--new_gen_semi_max_size=2
 
 import 'dart:_internal' show VMInternalsForTesting;
 import 'dart:developer';
 
@@ -155,7 +155,7 @@ constexpr bool FLAG_support_il_printer = false;
   P(modular_aot_mode, bool, false, "Modular AOT compiler mode")                \
   P(new_gen_semi_max_size, int, kDefaultNewGenSemiMaxSize,                     \
     "Max size of new gen semi space in MB")                                    \
-  P(new_gen_semi_initial_size, int, (kWordSize <= 4) ? 1 : 2,                  \
+  P(new_gen_semi_initial_size, int, (kWordSize <= 4) ? 2 : 4,                  \
     "Initial size of new gen semi space in MB")                                \
   P(optimization_counter_threshold, int, kDefaultOptimizationCounterThreshold, \
     "Function's usage-counter value before it is optimized, -1 means never")   \
 
@@ -5,6 +5,7 @@
 #include "vm/flags.h"
 
 #include "platform/assert.h"
+#include "vm/heap/page.h"
 #include "vm/isolate.h"
 #include "vm/json_stream.h"
 #include "vm/os.h"
@@ -559,6 +560,13 @@ char* Flags::CheckFlags() {
     return Utils::StrDup("Invalid compactor_tasks");
   }
 
+  if (FLAG_new_gen_semi_initial_size * MB < Page::kPageSize) {
+    return Utils::StrDup("Invalid new_gen_semi_initial_size");
+  }
+  if (FLAG_new_gen_semi_max_size * MB < Page::kPageSize) {
+    return Utils::StrDup("Invalid new_gen_semi_max_size");
+  }
+
   return nullptr;
 }
 
 
@@ -44,7 +44,7 @@ class Page {
   // object can be computed by masking the object with kPageMask.
   // This does not apply to image pages, whose address is chosen by the system
   // loader rather than the Dart VM.
-  static constexpr intptr_t kPageSize = 512 * KB;
+  static constexpr intptr_t kPageSize = 2 * MB;
   static constexpr intptr_t kPageSizeInWords = kPageSize / kWordSize;
   static constexpr intptr_t kPageMask = ~(kPageSize - 1);
 
@@ -342,7 +342,7 @@ class PageCache {
   // to fit a complete from-space into this cache. The standalone embedder sets
   // the semispace size to 16/32MB. This cache is in units of regular heap
   // pages, which are 512kB (Page::kPageSize).
-  static constexpr intptr_t kCapacity = 128 * kWordSize;
+  static constexpr intptr_t kCapacity = (4 * kWordSize * MB) / Page::kPageSize;
   Mutex mutex_;
   VirtualMemory* cache_[2][kCapacity] = {{nullptr}, {nullptr}};
   intptr_t size_[2] = {0, 0};
 
@@ -35,7 +35,7 @@ DEFINE_FLAG(int,
             "The desired maximum percentage of time spent in old gen GC");
 DEFINE_FLAG(int,
             old_gen_growth_rate,
-            280,
+            70,
             "The max number of pages the old generation can grow at a time");
 DEFINE_FLAG(bool, log_growth, false, "Log PageSpace growth policy decisions.");
 
 
@@ -1975,7 +1975,12 @@ void Scavenger::Scavenge(Thread* thread, GCType type, GCReason reason) {
   }
   SemiSpace* from = Prologue(reason);
 
-  const intptr_t num_tasks = NumScavengeWorkers();
+  intptr_t num_tasks = NumScavengeWorkers();
+  intptr_t max_pages = to_->gc_threshold_in_words() / Page::kPageSizeInWords;
+  ASSERT(max_pages >= 1);
+  if (num_tasks > max_pages) {
+    num_tasks = max_pages;
+  }
 
   ThreadBarrier* barrier = new ThreadBarrier(num_tasks, /*initial=*/1);
   RelaxedAtomic<uintptr_t> num_busy = 0;
 
@@ -131,6 +131,23 @@ static void* GenericMapAligned(void* hint,
     return reinterpret_cast<void*>(address);
   }
 #endif
+
+#if (defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_ANDROID)) &&          \
+    defined(ARCH_IS_64_BIT)
+  // Usually. Might be larger on some arm64 configurations.
+  constexpr intptr_t kSuperPageSize = 2 * MB;
+  if (alignment == kSuperPageSize) {
+    void* address = Map(nullptr, size, prot, map_flags, -1, 0);
+    if (address != MAP_FAILED) {
+      if (Utils::IsAligned(address, alignment)) [[likely]] {
+        madvise(address, size, MADV_HUGEPAGE);
+        return address;
+      }
+      munmap(address, size);
+    }
+  }
+#endif
+
   void* address = Map(hint, allocated_size, prot, map_flags, -1, 0);
   if (address == MAP_FAILED) {
     return nullptr;
@@ -573,25 +590,6 @@ void VirtualMemory::Init() {
   }
 #endif
 #endif
-
-#if defined(DART_HOST_OS_LINUX) || defined(DART_HOST_OS_ANDROID)
-  FILE* fp = fopen("/proc/sys/vm/max_map_count", "r");
-  if (fp != nullptr) {
-    size_t max_map_count = 0;
-    int count = fscanf(fp, "%zu", &max_map_count);
-    fclose(fp);
-    if (count == 1) {
-      size_t max_heap_pages = FLAG_old_gen_heap_size * MB / Page::kPageSize;
-      if (max_map_count < max_heap_pages) {
-        OS::PrintErr(
-            "warning: vm.max_map_count (%zu) is not large enough to support "
-            "--old_gen_heap_size=%d. Consider increasing it with `sysctl -w "
-            "vm.max_map_count=%zu`\n",
-            max_map_count, FLAG_old_gen_heap_size, max_heap_pages);
-      }
-    }
-  }
-#endif
 }
 
 void VirtualMemory::Cleanup() {