I found the dearth of comments in morecore.c to be quite troublesome
while debugging a related kernel bug. I hope these are accurate.
Signed-off-by: Nishanth Aravamudan <[EMAIL PROTECTED]>
diff -urpN a/morecore.c b/morecore.c
--- a/morecore.c 2006-09-06 11:34:18.000000000 -0700
+++ b/morecore.c 2006-09-06 11:58:48.000000000 -0700
@@ -92,16 +92,26 @@ static void *hugetlbfs_morecore(ptrdiff_
DEBUG("hugetlbfs_morecore(%ld) = ...\n", (long)increment);
+ /*
+ * how much to grow the heap by =
+ * (size of heap) + malloc request - mmap'd space
+ */
newsize = (heaptop-heapbase) + increment - mapsize;
DEBUG("heapbase = %p, heaptop = %p, mapsize = %lx, newsize=%ld\n",
heapbase, heaptop, mapsize, newsize);
+ /* growing the heap */
if (newsize > 0) {
+ /*
+ * convert our request to a multiple of hugepages
+ * we will have more space allocated then used, basically
+ */
newsize = ALIGN(newsize, blocksize);
DEBUG("Attempting to map %ld bytes\n", newsize);
+ /* map in (extend) more of the file at the end of our last map
*/
p = mmap(heapbase + mapsize, newsize, PROT_READ|PROT_WRITE,
MAP_PRIVATE, heap_fd, mapsize);
if (p == MAP_FAILED) {
@@ -109,10 +119,12 @@ static void *hugetlbfs_morecore(ptrdiff_
return NULL;
}
+ /* if this is the first map */
if (! mapsize) {
if (heapbase && (heapbase != p))
WARNING("Heap originates at %p instead of %p\n",
p, heapbase);
+ /* then setup the heap variables */
heapbase = heaptop = p;
} else if (p != (heapbase + mapsize)) {
/* Couldn't get the mapping where we wanted */
@@ -130,10 +142,13 @@ static void *hugetlbfs_morecore(ptrdiff_
return NULL;
}
+ /* we now have mmap'd further */
mapsize += newsize;
}
+ /* heap is continuous */
p = heaptop;
+ /* and we now have added this much more space to the heap */
heaptop = heaptop + increment;
DEBUG("... = %p\n", p);
--
Nishanth Aravamudan <[EMAIL PROTECTED]>
IBM Linux Technology Center
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