diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7f880f74..bc4b3a51 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -176,7 +176,7 @@ endif()
 
 # Compiler flags
 if(CMAKE_C_COMPILER_ID MATCHES "AppleClang|Clang|GNU")
-  list(APPEND mi_cflags -Wall -Wextra -Wno-unknown-pragmas -fvisibility=hidden)
+  list(APPEND mi_cflags -Wall -Wextra -Wno-unknown-pragmas -fvisibility=hidden   $<$<CONFIG:RELEASE>:-O3>)
   if(NOT MI_USE_CXX)
     list(APPEND mi_cflags -Wstrict-prototypes)
   endif()
diff --git a/include/mimalloc-internal.h b/include/mimalloc-internal.h
index 4e05c724..12d050f7 100644
--- a/include/mimalloc-internal.h
+++ b/include/mimalloc-internal.h
@@ -497,6 +497,10 @@ static inline size_t mi_segment_size(mi_segment_t* segment) {
   return segment->segment_slices * MI_SEGMENT_SLICE_SIZE;
 }
 
+static inline uint8_t* mi_segment_end(mi_segment_t* segment) {
+  return (uint8_t*)segment + mi_segment_size(segment);
+}
+
 // Thread free access
 static inline mi_block_t* mi_page_thread_free(const mi_page_t* page) {
   return (mi_block_t*)(mi_atomic_load_relaxed(&((mi_page_t*)page)->xthread_free) & ~3);
diff --git a/src/options.c b/src/options.c
index 925ecbf9..859b3871 100644
--- a/src/options.c
+++ b/src/options.c
@@ -66,7 +66,7 @@ static mi_option_desc_t options[_mi_option_last] =
   { 0, UNINIT, MI_OPTION(verbose) },
 
   // the following options are experimental and not all combinations make sense.
-  { 0, UNINIT, MI_OPTION(eager_commit) },        // commit per segment directly (8MiB)  (but see also `eager_commit_delay`)
+  { 1, UNINIT, MI_OPTION(eager_commit) },        // commit per segment directly (8MiB)  (but see also `eager_commit_delay`)
   #if defined(_WIN32) || (MI_INTPTR_SIZE <= 4)   // and other OS's without overcommit?
   { 0, UNINIT, MI_OPTION(eager_region_commit) },
   { 0, UNINIT, MI_OPTION(reset_decommits) },     // reset decommits memory
@@ -89,7 +89,7 @@ static mi_option_desc_t options[_mi_option_last] =
   { 1, UNINIT, MI_OPTION(eager_commit_delay) },  // the first N segments per thread are not eagerly committed (but per page in the segment on demand)
 #endif
   { 1,    UNINIT, MI_OPTION(allow_decommit) },    // decommit slices when no longer used (after reset_delay milli-seconds)
-  { 100,  UNINIT, MI_OPTION(reset_delay) },       // page reset delay in milli-seconds (= decommit)
+  { 25,   UNINIT, MI_OPTION(reset_delay) },       // page reset delay in milli-seconds (= decommit)
   { 500,  UNINIT, MI_OPTION(segment_decommit_delay) },// decommit delay in milli-seconds for freed segments
   { 0,    UNINIT, MI_OPTION(use_numa_nodes) },    // 0 = use available numa nodes, otherwise use at most N nodes. 
   { 0,    UNINIT, MI_OPTION(limit_os_alloc) },    // 1 = do not use OS memory for allocation (but only reserved arenas)
diff --git a/src/segment.c b/src/segment.c
index 93548f24..a80ae9c4 100644
--- a/src/segment.c
+++ b/src/segment.c
@@ -448,7 +448,8 @@ static void mi_segment_commit_mask(mi_segment_t* segment, bool conservative, uin
   mi_assert_internal(_mi_ptr_segment(p) == segment);
   mi_commit_mask_create_empty(cm);
   if (size == 0 || size > MI_SEGMENT_SIZE) return;
-  if (p >= (uint8_t*)segment + mi_segment_size(segment)) return;
+  const ptrdiff_t segsize = (ptrdiff_t)mi_segment_size(segment);
+  if (p >= (uint8_t*)segment + segsize) return;
 
   ptrdiff_t diff = (p - (uint8_t*)segment);
   ptrdiff_t start;
@@ -461,6 +462,10 @@ static void mi_segment_commit_mask(mi_segment_t* segment, bool conservative, uin
     start = _mi_aligni_down(diff, MI_COMMIT_SIZE);
     end   = _mi_aligni_up(diff + size, MI_COMMIT_SIZE);
   }
+  mi_assert_internal(end <= segsize);
+  if (end > segsize) {
+    end = segsize;
+  }
 
   mi_assert_internal(start % MI_COMMIT_SIZE==0 && end % MI_COMMIT_SIZE == 0);
   *start_p   = (uint8_t*)segment + start;
@@ -478,9 +483,14 @@ static void mi_segment_commit_mask(mi_segment_t* segment, bool conservative, uin
   mi_commit_mask_create(bitidx, bitcount, cm);
 }
 
+#define MI_COMMIT_SIZE_BATCH  MiB
+
 static bool mi_segment_commitx(mi_segment_t* segment, bool commit, uint8_t* p, size_t size, mi_stats_t* stats) {    
   mi_assert_internal(mi_commit_mask_all_set(&segment->commit_mask, &segment->decommit_mask));
 
+  //if (commit && size < MI_COMMIT_SIZE_BATCH && p + MI_COMMIT_SIZE_BATCH <= mi_segment_end(segment)) {
+  //  size = MI_COMMIT_SIZE_BATCH;
+  // }
   // commit liberal, but decommit conservative
   uint8_t* start = NULL;
   size_t   full_size = 0;
@@ -541,6 +551,21 @@ static void mi_segment_perhaps_decommit(mi_segment_t* segment, uint8_t* p, size_
     mi_commit_mask_create_intersect(&segment->commit_mask, &mask, &cmask);  // only decommit what is committed; span_free may try to decommit more
     mi_commit_mask_set(&segment->decommit_mask, &cmask);
     segment->decommit_expire = _mi_clock_now() + mi_option_get(mi_option_reset_delay);
+    mi_msecs_t now = _mi_clock_now();
+    if (segment->decommit_expire == 0) {
+      // no previous decommits, initialize now
+      mi_assert_internal(mi_commit_mask_is_empty(&segment->decommit_mask));
+      segment->decommit_expire = now + mi_option_get(mi_option_reset_delay);
+    }
+    else if (segment->decommit_expire <= now) {
+      // previous decommit mask already expired
+      // mi_segment_delayed_decommit(segment, true, stats);
+      segment->decommit_expire = now + 1;
+    }
+    else {
+      // previous decommit mask is not yet expired
+      // segment->decommit_expire++;
+    }
   }  
 }