hybrid allocator tuning

Set various pragmas and defines to tune the hybrid allocator.

Performance test was the time takes to allocate or deallocate as
appropriate 1,000,000 times from a set of 100,000 pointers, selected at
random, with sizes generated randomly with min 2, max 5960, avg 46.
The function was exp(8 - log(2 + rand(0..1023))) * rand(1 or 4).

The following parameters were chosen:
   * pragma arm, for ~1.2%
   * pragma Otime, for ~3%
   * pragma O2, already the compiler default, just to be sure
   * all possible slab sizes enabled, for ~1%

NB Disabling BTrace would also gain ~1.5%, but that seems like a bad
thing to do. Not done.

Task-number: QT-3967
Reviewed-by: Shane Kearns

1 files changed, 2 insertions, 1 deletions

diff --git a/src/corelib/arch/symbian/heap_hybrid.cpp b/src/corelib/arch/symbian/heap_hybrid.cpp
index 4d101ed23d..f650b5b52b 100644
--- a/src/corelib/arch/symbian/heap_hybrid.cpp
+++ b/src/corelib/arch/symbian/heap_hybrid.cpp
@@ -45,7 +45,8 @@
 
 // if non zero this causes the iSlabs to be configured only when the chunk size exceeds this level
 #define DELAYED_SLAB_THRESHOLD (64*1024)		// 64KB seems about right based on trace data
-#define SLAB_CONFIG 0xabe						// Use slabs of size 48, 40, 32, 24, 20, 16, 12, and 8 bytes
+//#define SLAB_CONFIG 0xabe						// Use slabs of size 48, 40, 32, 24, 20, 16, 12, and 8 bytes
+#define SLAB_CONFIG 0x3fff						// Use all slab sizes 4,8..56 bytes
 
 #ifdef _DEBUG
 #define __SIMULATE_ALLOC_FAIL(s)	if (CheckForSimulatedAllocFail()) {s}