io_u: don't do expensive int divide for buffer scramble

We don't need the conversion from nsec to usec to be exact, so
just shift by 10 instead.

Fixes: 8b6a404cd ("nanosecond: initial commit changing timeval to timespec")
Signed-off-by: Jens Axboe <axboe@kernel.dk>

diff --git a/io_u.c b/io_u.c
index 6b950014aa7cb6382d5ce2be00e18b30c745ba7f..e1e4495202cb22fe8e589541e8704a37f4e11d36 100644 (file)
--- a/io_u.c
+++ b/io_u.c
@@ -1673,7 +1673,7 @@ static bool check_get_verify(struct thread_data *td, struct io_u *io_u)
 static void small_content_scramble(struct io_u *io_u)
 {
        unsigned int i, nr_blocks = io_u->buflen / 512;
-       uint64_t boffset;
+       uint64_t boffset, usec;
        unsigned int offset;
        char *p, *end;
 
@@ -1684,13 +1684,16 @@ static void small_content_scramble(struct io_u *io_u)
        boffset = io_u->offset;
        io_u->buf_filled_len = 0;
 
+       /* close enough for this purpose */
+       usec = io_u->start_time.tv_nsec >> 10;
+
        for (i = 0; i < nr_blocks; i++) {
                /*
                 * Fill the byte offset into a "random" start offset of
                 * the buffer, given by the product of the usec time
                 * and the actual offset.
                 */
-               offset = ((io_u->start_time.tv_nsec/1000) ^ boffset) & 511;
+               offset = (usec ^ boffset) & 511;
                offset &= ~(sizeof(uint64_t) - 1);
                if (offset >= 512 - sizeof(uint64_t))
                        offset -= sizeof(uint64_t);