qemu-img: Speed up comparing empty/zero images
Two empty raw files are always compared by actually reading data even if there is no data, because BDRV_BLOCK_ZERO is considered "allocated" in bdrv_is_allocated_above(). That is inefficient. Use bdrv_get_block_status_above() for more information, and skip the consecutive zero sectors. This brings a huge speed up in comparing sparse/empty raw images: $ qemu-img create a 1G $ time ~/build/master/bin/qemu-img compare a a Images are identical. real 0m6.583s user 0m0.191s sys 0m6.367s $ time qemu-img compare a a Images are identical. real 0m0.033s user 0m0.003s sys 0m0.031s Signed-off-by: Fam Zheng <famz@redhat.com> Reviewed-by: Paolo Bonzini <pbonzini@redhat.com> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
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qemu-img.c
45
qemu-img.c
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@ -1071,28 +1071,50 @@ static int img_compare(int argc, char **argv)
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}
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}
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for (;;) {
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for (;;) {
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int64_t status1, status2;
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nb_sectors = sectors_to_process(total_sectors, sector_num);
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nb_sectors = sectors_to_process(total_sectors, sector_num);
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if (nb_sectors <= 0) {
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if (nb_sectors <= 0) {
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break;
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break;
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}
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}
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allocated1 = bdrv_is_allocated_above(bs1, NULL, sector_num, nb_sectors,
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status1 = bdrv_get_block_status_above(bs1, NULL, sector_num,
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&pnum1);
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total_sectors1 - sector_num,
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if (allocated1 < 0) {
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&pnum1);
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if (status1 < 0) {
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ret = 3;
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ret = 3;
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error_report("Sector allocation test failed for %s", filename1);
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error_report("Sector allocation test failed for %s", filename1);
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goto out;
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goto out;
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}
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}
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allocated1 = status1 & BDRV_BLOCK_ALLOCATED;
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allocated2 = bdrv_is_allocated_above(bs2, NULL, sector_num, nb_sectors,
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status2 = bdrv_get_block_status_above(bs2, NULL, sector_num,
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&pnum2);
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total_sectors2 - sector_num,
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if (allocated2 < 0) {
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&pnum2);
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if (status2 < 0) {
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ret = 3;
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ret = 3;
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error_report("Sector allocation test failed for %s", filename2);
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error_report("Sector allocation test failed for %s", filename2);
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goto out;
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goto out;
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}
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}
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nb_sectors = MIN(pnum1, pnum2);
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allocated2 = status2 & BDRV_BLOCK_ALLOCATED;
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if (pnum1) {
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nb_sectors = MIN(nb_sectors, pnum1);
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}
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if (pnum2) {
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nb_sectors = MIN(nb_sectors, pnum2);
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}
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if (allocated1 == allocated2) {
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if (strict) {
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if ((status1 & ~BDRV_BLOCK_OFFSET_MASK) !=
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(status2 & ~BDRV_BLOCK_OFFSET_MASK)) {
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ret = 1;
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qprintf(quiet, "Strict mode: Offset %" PRId64
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" block status mismatch!\n",
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sectors_to_bytes(sector_num));
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goto out;
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}
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}
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if ((status1 & BDRV_BLOCK_ZERO) && (status2 & BDRV_BLOCK_ZERO)) {
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nb_sectors = MIN(pnum1, pnum2);
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} else if (allocated1 == allocated2) {
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if (allocated1) {
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if (allocated1) {
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ret = blk_read(blk1, sector_num, buf1, nb_sectors);
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ret = blk_read(blk1, sector_num, buf1, nb_sectors);
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if (ret < 0) {
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if (ret < 0) {
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@ -1120,13 +1142,6 @@ static int img_compare(int argc, char **argv)
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}
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}
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}
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}
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} else {
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} else {
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if (strict) {
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ret = 1;
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qprintf(quiet, "Strict mode: Offset %" PRId64
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" allocation mismatch!\n",
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sectors_to_bytes(sector_num));
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goto out;
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}
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if (allocated1) {
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if (allocated1) {
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ret = check_empty_sectors(blk1, sector_num, nb_sectors,
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ret = check_empty_sectors(blk1, sector_num, nb_sectors,
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