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[Qemu-devel] [PATCH] qemu-img: Speed up comparing empty/zero images
From: |
Fam Zheng |
Subject: |
[Qemu-devel] [PATCH] qemu-img: Speed up comparing empty/zero images |
Date: |
Wed, 13 Jan 2016 16:37:41 +0800 |
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 <address@hidden>
---
qemu-img.c | 45 ++++++++++++++++++++++++++++++---------------
1 file changed, 30 insertions(+), 15 deletions(-)
diff --git a/qemu-img.c b/qemu-img.c
index 3d48b4f..82f704f 100644
--- a/qemu-img.c
+++ b/qemu-img.c
@@ -1074,28 +1074,50 @@ static int img_compare(int argc, char **argv)
}
for (;;) {
+ int64_t status1, status2;
nb_sectors = sectors_to_process(total_sectors, sector_num);
if (nb_sectors <= 0) {
break;
}
- allocated1 = bdrv_is_allocated_above(bs1, NULL, sector_num, nb_sectors,
- &pnum1);
- if (allocated1 < 0) {
+ status1 = bdrv_get_block_status_above(bs1, NULL, sector_num,
+ total_sectors1 - sector_num,
+ &pnum1);
+ if (status1 < 0) {
ret = 3;
error_report("Sector allocation test failed for %s", filename1);
goto out;
}
+ allocated1 = status1 & BDRV_BLOCK_ALLOCATED;
- allocated2 = bdrv_is_allocated_above(bs2, NULL, sector_num, nb_sectors,
- &pnum2);
- if (allocated2 < 0) {
+ status2 = bdrv_get_block_status_above(bs2, NULL, sector_num,
+ total_sectors2 - sector_num,
+ &pnum2);
+ if (status2 < 0) {
ret = 3;
error_report("Sector allocation test failed for %s", filename2);
goto out;
}
- nb_sectors = MIN(pnum1, pnum2);
+ allocated2 = status2 & BDRV_BLOCK_ALLOCATED;
+ if (pnum1) {
+ nb_sectors = MIN(nb_sectors, pnum1);
+ }
+ if (pnum2) {
+ nb_sectors = MIN(nb_sectors, pnum2);
+ }
- if (allocated1 == allocated2) {
+ if (strict) {
+ if ((status1 & ~BDRV_BLOCK_OFFSET_MASK) !=
+ (status2 & ~BDRV_BLOCK_OFFSET_MASK)) {
+ ret = 1;
+ qprintf(quiet, "Strict mode: Offset %" PRId64
+ " block status mismatch!\n",
+ sectors_to_bytes(sector_num));
+ goto out;
+ }
+ }
+ if ((status1 & BDRV_BLOCK_ZERO) && (status2 & BDRV_BLOCK_ZERO)) {
+ nb_sectors = MIN(pnum1, pnum2);
+ } else if (allocated1 == allocated2) {
if (allocated1) {
ret = blk_read(blk1, sector_num, buf1, nb_sectors);
if (ret < 0) {
@@ -1123,13 +1145,6 @@ static int img_compare(int argc, char **argv)
}
}
} else {
- if (strict) {
- ret = 1;
- qprintf(quiet, "Strict mode: Offset %" PRId64
- " allocation mismatch!\n",
- sectors_to_bytes(sector_num));
- goto out;
- }
if (allocated1) {
ret = check_empty_sectors(blk1, sector_num, nb_sectors,
--
2.4.3
- [Qemu-devel] [PATCH] qemu-img: Speed up comparing empty/zero images,
Fam Zheng <=