Hi,
If the elements argument passed to hashinit() is a power of 2 there's no
need to find the closest power of 2 that can fit all elements since
elements == hashsize will always be true. During boot of a stock amd64
kernel running inside vmd 80% of the calls to hashinit() includes a
power of 2 size.
Comments? OK?
Index: kern/kern_subr.c
===================================================================
RCS file: /cvs/src/sys/kern/kern_subr.c,v
retrieving revision 1.49
diff -u -p -r1.49 kern_subr.c
--- kern/kern_subr.c 14 Feb 2017 10:31:15 -0000 1.49
+++ kern/kern_subr.c 28 Apr 2018 20:21:40 -0000
@@ -163,8 +163,11 @@ hashinit(int elements, int type, int fla
if (elements <= 0)
panic("hashinit: bad cnt");
- for (hashsize = 1; hashsize < elements; hashsize <<= 1)
- continue;
+ if ((elements & (elements - 1)) == 0)
+ hashsize = elements;
+ else
+ for (hashsize = 1; hashsize < elements; hashsize <<= 1)
+ continue;
hashtbl = mallocarray(hashsize, sizeof(*hashtbl), type, flags);
if (hashtbl == NULL)
return NULL;
