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J. Templ heap tweaks - improved handling in extreme memory scenarios.

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This commit is contained in:
David Brown 2016-12-29 15:28:04 +00:00
parent 6a20f8f951
commit 0666629e1e
1 changed files with 24 additions and 14 deletions
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38
src/runtime/Heap.Mod
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@ -10,7 +10,6 @@ MODULE Heap;
Unit = 4*SZA; (* Smallest possible heap block *)
nofLists = 9; (* Number of freelist entries excluding sentinel *)
heapSize0 = 8000*Unit; (* Startup heap size *)
heapMinExpand = 10000*Unit; (* minimum heap expansion size *)
(* all blocks look the same:
free blocks describe themselves: size = Unit
@ -83,10 +82,11 @@ MODULE Heap;
(* extensible heap *)
heap-: S.ADDRESS; (* the sorted list of heap chunks *)
heapMin: S.ADDRESS; (* Range of valid pointer values, used for stack collection *)
heapMax: S.ADDRESS;
heapsize*: S.ADDRESS; (* the sum of all heap chunk sizes *)
heap-: S.ADDRESS; (* the sorted list of heap chunks *)
heapMin: S.ADDRESS; (* Range of valid pointer values, used for stack collection *)
heapMax: S.ADDRESS;
heapsize*: S.ADDRESS; (* the sum of all heap chunk sizes *)
heapMinExpand*: S.ADDRESS; (* minimum heap expansion size *)
(* finalization candidates *)
fin: FinNode;
@ -213,6 +213,7 @@ MODULE Heap;
PROCEDURE ExtendHeap(blksz: S.ADDRESS);
VAR size, chnk, j, next: S.ADDRESS;
BEGIN
ASSERT(blksz MOD Unit = 0);
IF uLT(heapMinExpand, blksz) THEN size := blksz
ELSE size := heapMinExpand (* additional heuristics for avoiding many small heap expansions *)
END;
@ -229,6 +230,12 @@ MODULE Heap;
END;
S.PUT(chnk, next); S.PUT(j, chnk)
END
ELSIF ~firstTry THEN
(* Heap memory exhausted, i.e. heap is not expanded and NEWREC() will return NIL.
In order to be able to report a trap due to NIL access, there is more
memory needed, which may be available by reducing heapMinExpand. *)
heapMinExpand := Unit
(* ELSE firstTry: ignore failed heap expansion for anti-thrashing heuristics. *)
END
END ExtendHeap;
@ -270,8 +277,10 @@ MODULE Heap;
IF firstTry THEN
GC(TRUE); INC(blksz, Unit);
(* Anti-thrashing heuristics: ensure 1/5 of the heap will not be allocated. *)
t := S.LSH(allocated + blksz, -(ldUnit+2)) (*uDIV 4*Unit*) * (5*Unit) ; (* Minimum preferred heapsize *)
IF uLT(heapsize, t) THEN ExtendHeap(t - heapsize) END;
t := S.LSH(allocated + blksz, -(2+ldUnit)) (*uDIV 4*Unit*) * (5*Unit) ; (* Minimum preferred heapsize *)
IF uLT(heapsize, t) THEN ExtendHeap(t - heapsize)
(* If there is not enough heap memory then the heap will be expanded below by blksz *)
END;
firstTry := FALSE; new := NEWREC(tag);
IF new = NIL THEN (* Heap is 1/5 free but fragmentation prevented allocation *)
ExtendHeap(blksz);
@ -592,13 +601,14 @@ MODULE Heap;
(* InitHeap is called by Platform.init before any module bodies have been
initialised, to enable NEW, S.NEW *)
BEGIN
heap := 0;
heapsize := 0;
allocated := 0;
lockdepth := 0;
heapMin := -1; (* all bits set *)
heapMax := 0;
bigBlocks := 0;
heap := 0;
heapsize := 0;
allocated := 0;
lockdepth := 0;
heapMin := -1; (* all bits set = max unsigned value *)
heapMax := 0;
bigBlocks := 0;
heapMinExpand := heapSize0;
ASSERT((Unit = 16) OR (Unit = 32));
IF Unit = 16 THEN ldUnit := 4 ELSE ldUnit := 5 END;