From 79db54e084272614e80e5e876c107aca65bd2a89 Mon Sep 17 00:00:00 2001
From: Stewart Brodie <sbrodie@gitlab.riscosopen.org>
Date: Tue, 5 Jun 2001 09:20:05 +0000
Subject: [PATCH] Minor optimisation to the heap manager for performance
enhancement.
Detail:
When splitting a free block in order to satisfy an allocation request,
don't split if the remaining free space falls below a specified
threshold (<= 8 bytes) to avoid creating lots of tiny free blocks,
but instead gift the extra 8 bytes to the newly allocated block.
This should stop the worst case heap fragmentation seen with OS_Heap
heaps (particular the Toolbox's dynamic area).
Admin:
Tested in Ursula desktop build.
Version 5.44. Tagged as 'Kernel-5_44'
---
VersionASM | 14 +++++++-------
VersionNum | 20 ++++++++++----------
s/HeapMan | 18 ++++++++++++++++++
3 files changed, 35 insertions(+), 17 deletions(-)
diff --git a/VersionASM b/VersionASM
index 575eb181..699b6bc4 100644
--- a/VersionASM
+++ b/VersionASM
@@ -11,14 +11,14 @@
GBLS Module_HelpVersion
GBLS Module_ComponentName
GBLS Module_ComponentPath
-Module_MajorVersion SETS "5.43"
-Module_Version SETA 543
+Module_MajorVersion SETS "5.44"
+Module_Version SETA 544
Module_MinorVersion SETS ""
-Module_Date SETS "25 May 2001"
-Module_ApplicationDate2 SETS "25-May-01"
-Module_ApplicationDate4 SETS "25-May-2001"
+Module_Date SETS "05 Jun 2001"
+Module_ApplicationDate2 SETS "05-Jun-01"
+Module_ApplicationDate4 SETS "05-Jun-2001"
Module_ComponentName SETS "Kernel"
Module_ComponentPath SETS "RiscOS/Sources/Kernel"
-Module_FullVersion SETS "5.43"
-Module_HelpVersion SETS "5.43 (25 May 2001)"
+Module_FullVersion SETS "5.44"
+Module_HelpVersion SETS "5.44 (05 Jun 2001)"
END
diff --git a/VersionNum b/VersionNum
index f903c298..d377d733 100644
--- a/VersionNum
+++ b/VersionNum
@@ -1,22 +1,22 @@
-/* (5.43)
+/* (5.44)
*
* This file is automatically maintained by srccommit, do not edit manually.
*
*/
-#define Module_MajorVersion_CMHG 5.43
+#define Module_MajorVersion_CMHG 5.44
#define Module_MinorVersion_CMHG
-#define Module_Date_CMHG 25 May 2001
+#define Module_Date_CMHG 05 Jun 2001
-#define Module_MajorVersion "5.43"
-#define Module_Version 543
+#define Module_MajorVersion "5.44"
+#define Module_Version 544
#define Module_MinorVersion ""
-#define Module_Date "25 May 2001"
+#define Module_Date "05 Jun 2001"
-#define Module_ApplicationDate2 "25-May-01"
-#define Module_ApplicationDate4 "25-May-2001"
+#define Module_ApplicationDate2 "05-Jun-01"
+#define Module_ApplicationDate4 "05-Jun-2001"
#define Module_ComponentName "Kernel"
#define Module_ComponentPath "RiscOS/Sources/Kernel"
-#define Module_FullVersion "5.43"
-#define Module_HelpVersion "5.43 (25 May 2001)"
+#define Module_FullVersion "5.44"
+#define Module_HelpVersion "5.44 (05 Jun 2001)"
diff --git a/s/HeapMan b/s/HeapMan
index 3438d37c..3bb0b147 100644
--- a/s/HeapMan
+++ b/s/HeapMan
@@ -109,6 +109,16 @@ freblksize # 0
; They must also be capable of storing a 4 byte size field while allocated.
; This field is used to size the block to free when FreeArea is called.
+; This is the threshold for minimum heap block fragmentation size. Splitting a
+; free block won't leave a free block which is <= than the size declared here.
+; If by choosing to use a particular free block, allocating a new block would
+; leave a free block of this size or less, add it on to the original size request
+; to avoid generating lots of silly little blocks that slow things down so much.
+; This value must not be too large because non-C callers may extend the block
+; piecemeal based on their (now wrong) knowledge of the block size. The C library
+; reads the block size straight out of the heap block data, and will thus not
+; be fooled.
+minheapfragsize # 8
ALIGN
@@ -605,6 +615,14 @@ garloop
SUBS HpTemp, HpTemp, size ; In case this works, for below split
BLO garloop
+;
+; Try and stop very small blocks appearing due to fragmentation - if we fitted with
+; a minimal amount of overhead, pretend we had an exact match
+;
+ CMPNE HpTemp, #minheapfragsize+1 ; set LO if we can salvage this tiny block
+ ADDLO size, size, HpTemp ; increment the size to encompass the block
+ MOVLOS HpTemp, #0 ; pretend we fitted exactly, set EQ
+
; Now addr -> a block on the free space list that our item will fit in
; If we have an exact fit (or as close as the granularity of the free list will
; allow), unlink this block and return it
--
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