Micro-optimizations and comment fixes on the mem5.c memory allocator module.

FossilOrigin-Name: 8bf5e056eb8beb6e0ed5874fb24d7fe9f0b66d2b

manifest

@@ -1,5 +1,5 @@
-C Fix\sthe\sspellfix1_scriptcode()\sfunction\sto\signore\swhitespace\sand\spunctuation,\nand\sto\srecognize\shebrew\sand\sarabic\sscripts.
-D 2015-12-17T14:18:21.904
+C Micro-optimizations\sand\scomment\sfixes\son\sthe\smem5.c\smemory\sallocator\smodule.
+D 2015-12-18T16:29:47.912
 F Makefile.in 28bcd6149e050dff35d4dcfd97e890cd387a499d
 F Makefile.linux-gcc 7bc79876b875010e8c8f9502eb935ca92aa3c434
 F Makefile.msc 5fff077fcc46de7714ed6eebb6159a4c00eab751
@@ -304,7 +304,7 @@ F src/mem0.c 6a55ebe57c46ca1a7d98da93aaa07f99f1059645
 F src/mem1.c 6919bcf12f221868ea066eec27e579fed95ce98b
 F src/mem2.c f1940d9e91948dd6a908fbb9ce3835c36b5d83c3
 F src/mem3.c 8768ac94694f31ffaf8b4d0ea5dc08af7010a35a
-F src/mem5.c 5c267678ba9f745a2ee58102a9f482d64a58577a
+F src/mem5.c 262055c242fa7db59c5f07ad77fdc4e97888c054
 F src/memjournal.c 3eb2c0b51adbd869cb6a44780323f05fa904dc85
 F src/msvc.h d9ba56c6851227ab44b3f228a35f3f5772296495
 F src/mutex.c 8e45800ee78e0cd1f1f3fe8e398853307f4a085c
@@ -1405,7 +1405,7 @@ F tool/vdbe_profile.tcl 246d0da094856d72d2c12efec03250d71639d19f
 F tool/warnings-clang.sh f6aa929dc20ef1f856af04a730772f59283631d4
 F tool/warnings.sh 48bd54594752d5be3337f12c72f28d2080cb630b
 F tool/win/sqlite.vsix deb315d026cc8400325c5863eef847784a219a2f
-P 85ebd46c701e0a094a4690cd8f1d0cbae9aa257c
-R 70cdc580d7d9b92b032d33f5e0d50f2e
+P 7adfa4a5794e47f97491c08abeaaac90e826b331
+R 1b3cde8c2a6658c08ed08e4868245c5a
 U drh
-Z 6d4b5ed9cd1870281d7d851922f323d8
+Z 526b8930cb4e95afc320a389b1027b99

manifest.uuid

@@ -1 +1 @@
-7adfa4a5794e47f97491c08abeaaac90e826b331
+8bf5e056eb8beb6e0ed5874fb24d7fe9f0b66d2b

src/mem5.c

@@ -25,7 +25,7 @@
 **
 ** This memory allocator uses the following algorithm:
 **
-**   1.  All memory allocations sizes are rounded up to a power of 2.
+**   1.  All memory allocation sizes are rounded up to a power of 2.
 **
 **   2.  If two adjacent free blocks are the halves of a larger block,
 **       then the two blocks are coalesced into the single larger block.
@@ -117,7 +117,7 @@ static SQLITE_WSD struct Mem5Global {
   /*
   ** Lists of free blocks.  aiFreelist[0] is a list of free blocks of
   ** size mem5.szAtom.  aiFreelist[1] holds blocks of size szAtom*2.
-  ** and so forth.
+  ** aiFreelist[2] holds free blocks of size szAtom*4.  And so forth.
   */
   int aiFreelist[LOGMAX+1];
 
@@ -183,9 +183,7 @@ static void memsys5Link(int i, int iLogsize){
 }
 
 /*
-** If the STATIC_MEM mutex is not already held, obtain it now. The mutex
-** will already be held (obtained by code in malloc.c) if
-** sqlite3GlobalConfig.bMemStat is true.
+** Obtain or release the mutex needed to access global data structures.
 */
 static void memsys5Enter(void){
   sqlite3_mutex_enter(mem5.mutex);
@@ -195,9 +193,8 @@ static void memsys5Leave(void){
 }
 
 /*
-** Return the size of an outstanding allocation, in bytes.  The
-** size returned omits the 8-byte header overhead.  This only
-** works for chunks that are currently checked out.
+** Return the size of an outstanding allocation, in bytes.
+** This only works for chunks that are currently checked out.
 */
 static int memsys5Size(void *p){
   int iSize, i;
@@ -230,14 +227,10 @@ static void *memsys5MallocUnsafe(int nByte){
   /* Keep track of the maximum allocation request.  Even unfulfilled
   ** requests are counted */
   if( (u32)nByte>mem5.maxRequest ){
-    mem5.maxRequest = nByte;
-  }
-
     /* Abort if the requested allocation size is larger than the largest
-  ** power of two that we can represent using 32-bit signed integers.
-  */
-  if( nByte > 0x40000000 ){
-    return 0;
+    ** power of two that we can represent using 32-bit signed integers. */
+    if( nByte > 0x40000000 ) return 0;
+    mem5.maxRequest = nByte;
   }
 
   /* Round nByte up to the next valid power of two */
@@ -398,13 +391,11 @@ static void *memsys5Realloc(void *pPrior, int nBytes){
   if( nBytes<=nOld ){
     return pPrior;
   }
-  memsys5Enter();
-  p = memsys5MallocUnsafe(nBytes);
+  p = memsys5Malloc(nBytes);
   if( p ){
     memcpy(p, pPrior, nOld);
-    memsys5FreeUnsafe(pPrior);
+    memsys5Free(pPrior);
   }
-  memsys5Leave();
   return p;
 }