Author: dougm
Date: Sat May 11 02:13:52 2019
New Revision: 347477
URL: https://svnweb.freebsd.org/changeset/base/347477
Log:
Revert r347469.
Approved by: kib (mentor)
Modified:
head/sys/kern/subr_blist.c
Modified: head/sys/kern/subr_blist.c
==============================================================================
--- head/sys/kern/subr_blist.c Fri May 10 23:52:17 2019 (r347476)
+++ head/sys/kern/subr_blist.c Sat May 11 02:13:52 2019 (r347477)
@@ -192,41 +192,31 @@ bitrange(int n, int count)
/*
- * Find the first bit set in a u_daddr_t.
+ * Use binary search, or a faster method, to find the 1 bit in a u_daddr_t.
+ * Assumes that the argument has only one bit set.
*/
static inline int
-generic_bitpos(u_daddr_t mask)
+bitpos(u_daddr_t mask)
{
int hi, lo, mid;
- lo = 0;
- hi = BLIST_BMAP_RADIX;
- while (lo + 1 < hi) {
- mid = (lo + hi) >> 1;
- if (mask & bitrange(0, mid))
- hi = mid;
- else
- lo = mid;
- }
- return (lo);
-}
-
-static inline int
-bitpos(u_daddr_t mask)
-{
-
- switch (sizeof(mask)) {
+ switch (sizeof(mask)) {
#ifdef HAVE_INLINE_FFSLL
- case sizeof(long long):
- return (ffsll(mask) - 1);
+ case sizeof(long long):
+ return (ffsll(mask) - 1);
#endif
-#ifdef HAVE_INLINE_FFS
- case sizeof(int):
- return (ffs(mask) - 1);
-#endif
- default:
- return (generic_bitpos(mask));
- }
+ default:
+ lo = 0;
+ hi = BLIST_BMAP_RADIX;
+ while (lo + 1 < hi) {
+ mid = (lo + hi) >> 1;
+ if ((mask >> mid) != 0)
+ lo = mid;
+ else
+ hi = mid;
+ }
+ return (lo);
+ }
}
/*
@@ -542,8 +532,7 @@ blist_stats(blist_t bl, struct sbuf *s)
struct gap_stats gstats;
struct gap_stats *stats = &gstats;
daddr_t i, nodes, radix;
- u_daddr_t diff, mask;
- int digit;
+ u_daddr_t bit, diff, mask;
init_gap_stats(stats);
nodes = 0;
@@ -581,9 +570,9 @@ blist_stats(blist_t bl, struct sbuf *s)
if (gap_stats_counting(stats))
diff ^= 1;
while (diff != 0) {
- digit = bitpos(diff);
- update_gap_stats(stats, i + digit);
- diff ^= bitrange(digit, 1);
+ bit = diff & -diff;
+ update_gap_stats(stats, i + bitpos(bit));
+ diff ^= bit;
}
}
nodes += radix_to_skip(radix);
@@ -787,7 +776,7 @@ static daddr_t
blst_meta_alloc(blmeta_t *scan, daddr_t cursor, daddr_t count, u_daddr_t radix)
{
daddr_t blk, i, r, skip;
- u_daddr_t mask;
+ u_daddr_t bit, mask;
bool scan_from_start;
int digit;
@@ -819,7 +808,8 @@ blst_meta_alloc(blmeta_t *scan, daddr_t cursor, daddr_
* Examine the nonempty subtree associated with each bit set in mask.
*/
do {
- digit = bitpos(mask);
+ bit = mask & -mask;
+ digit = bitpos(bit);
i = 1 + digit * skip;
if (count <= scan[i].bm_bighint) {
/*
@@ -829,12 +819,12 @@ blst_meta_alloc(blmeta_t *scan, daddr_t cursor, daddr_
count, radix);
if (r != SWAPBLK_NONE) {
if (scan[i].bm_bitmap == 0)
- scan->bm_bitmap ^= bitrange(digit, 1);
+ scan->bm_bitmap ^= bit;
return (r);
}
}
cursor = blk;
- } while ((mask ^= bitrange(digit, 1)) != 0);
+ } while ((mask ^= bit) != 0);
/*
* We couldn't allocate count in this subtree. If the whole tree was
@@ -1029,7 +1019,7 @@ static void
blst_radix_print(blmeta_t *scan, daddr_t blk, daddr_t radix, int tab)
{
daddr_t skip;
- u_daddr_t mask;
+ u_daddr_t bit, mask;
int digit;
if (radix == BLIST_BMAP_RADIX) {
@@ -1061,10 +1051,11 @@ blst_radix_print(blmeta_t *scan, daddr_t blk, daddr_t
mask = scan->bm_bitmap;
/* Examine the nonempty subtree associated with each bit set in mask */
do {
- digit = bitpos(mask);
+ bit = mask & -mask;
+ digit = bitpos(bit);
blst_radix_print(&scan[1 + digit * skip], blk + digit * radix,
radix, tab);
- } while ((mask ^= bitrange(digit, 1)) != 0);
+ } while ((mask ^= bit) != 0);
tab -= 4;
printf(
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