diff options
Diffstat (limited to 'qemu-img.c')
| -rw-r--r-- | qemu-img.c | 35 |
1 files changed, 29 insertions, 6 deletions
diff --git a/qemu-img.c b/qemu-img.c index e8251234b1..4f162d1abe 100644 --- a/qemu-img.c +++ b/qemu-img.c @@ -496,14 +496,37 @@ static int img_commit(int argc, char **argv) return 0; } +/* + * Checks whether the sector is not a zero sector. + * + * Attention! The len must be a multiple of 4 * sizeof(long) due to + * restriction of optimizations in this function. + */ static int is_not_zero(const uint8_t *sector, int len) { + /* + * Use long as the biggest available internal data type that fits into the + * CPU register and unroll the loop to smooth out the effect of memory + * latency. + */ + int i; - len >>= 2; - for(i = 0;i < len; i++) { - if (((uint32_t *)sector)[i] != 0) + long d0, d1, d2, d3; + const long * const data = (const long *) sector; + + len /= sizeof(long); + + for(i = 0; i < len; i += 4) { + d0 = data[i + 0]; + d1 = data[i + 1]; + d2 = data[i + 2]; + d3 = data[i + 3]; + + if (d0 || d1 || d2 || d3) { return 1; + } } + return 0; } @@ -785,7 +808,7 @@ static int img_convert(int argc, char **argv) nb_sectors = total_sectors; local_progress = (float)100 / - (nb_sectors / MIN(nb_sectors, (cluster_sectors))); + (nb_sectors / MIN(nb_sectors, cluster_sectors)); for(;;) { int64_t bs_num; @@ -856,7 +879,7 @@ static int img_convert(int argc, char **argv) sector_num = 0; // total number of sectors converted so far nb_sectors = total_sectors - sector_num; local_progress = (float)100 / - (nb_sectors / MIN(nb_sectors, (IO_BUF_SIZE / 512))); + (nb_sectors / MIN(nb_sectors, IO_BUF_SIZE / 512)); for(;;) { nb_sectors = total_sectors - sector_num; @@ -1331,7 +1354,7 @@ static int img_rebase(int argc, char **argv) bdrv_get_geometry(bs, &num_sectors); local_progress = (float)100 / - (num_sectors / MIN(num_sectors, (IO_BUF_SIZE / 512))); + (num_sectors / MIN(num_sectors, IO_BUF_SIZE / 512)); for (sector = 0; sector < num_sectors; sector += n) { /* How many sectors can we handle with the next read? */ |