diff options
Diffstat (limited to 'net/ceph/crush/mapper.c')
| -rw-r--r-- | net/ceph/crush/mapper.c | 17 |
1 files changed, 11 insertions, 6 deletions
diff --git a/net/ceph/crush/mapper.c b/net/ceph/crush/mapper.c index 5fcfb98f309e..a421e905331a 100644 --- a/net/ceph/crush/mapper.c +++ b/net/ceph/crush/mapper.c @@ -245,7 +245,7 @@ static int bucket_straw_choose(struct crush_bucket_straw *bucket, /* compute 2^44*log2(input+1) */ static __u64 crush_ln(unsigned int xin) { - unsigned int x = xin, x1; + unsigned int x = xin; int iexpon, index1, index2; __u64 RH, LH, LL, xl64, result; @@ -253,9 +253,15 @@ static __u64 crush_ln(unsigned int xin) /* normalize input */ iexpon = 15; - while (!(x & 0x18000)) { - x <<= 1; - iexpon--; + + /* + * figure out number of bits we need to shift and + * do it in one step instead of iteratively + */ + if (!(x & 0x18000)) { + int bits = __builtin_clz(x & 0x1FFFF) - 16; + x <<= bits; + iexpon = 15 - bits; } index1 = (x >> 8) << 1; @@ -267,12 +273,11 @@ static __u64 crush_ln(unsigned int xin) /* RH*x ~ 2^48 * (2^15 + xf), xf<2^8 */ xl64 = (__s64)x * RH; xl64 >>= 48; - x1 = xl64; result = iexpon; result <<= (12 + 32); - index2 = x1 & 0xff; + index2 = xl64 & 0xff; /* LL ~ 2^48*log2(1.0+index2/2^15) */ LL = __LL_tbl[index2]; |