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[Qemu-devel] [PULL 01/31] block: split write_zeroes always
From: |
Kevin Wolf |
Subject: |
[Qemu-devel] [PULL 01/31] block: split write_zeroes always |
Date: |
Wed, 8 Jun 2016 11:16:27 +0200 |
From: "Denis V. Lunev" <address@hidden>
We should split requests even if they are less than write_zeroes_alignment.
For example we can have the following request:
offset 62k
size 4k
write_zeroes_alignment 64k
The original code sent 1 request covering 2 qcow2 clusters, and resulted
in both clusters being allocated. But by splitting the request, we can
cater to the case where one of the two clusters can be zeroed as a
whole, for only 1 cluster allocated after the operation.
Signed-off-by: Denis V. Lunev <address@hidden>
CC: Eric Blake <address@hidden>
CC: Kevin Wolf <address@hidden>
Message-Id: <address@hidden>
[eblake: Avoid exceeding nb_sectors, hoist alignment checks out of
loop, and update testsuite to show that patch works]
Signed-off-by: Eric Blake <address@hidden>
Reviewed-by: Fam Zheng <address@hidden>
Signed-off-by: Kevin Wolf <address@hidden>
---
block/io.c | 30 +++++++++++++++++-------------
tests/qemu-iotests/154.out | 18 ++++++++++++------
2 files changed, 29 insertions(+), 19 deletions(-)
diff --git a/block/io.c b/block/io.c
index 6070e77..c73be55 100644
--- a/block/io.c
+++ b/block/io.c
@@ -1118,28 +1118,32 @@ static int coroutine_fn
bdrv_co_do_write_zeroes(BlockDriverState *bs,
struct iovec iov = {0};
int ret = 0;
bool need_flush = false;
+ int head = 0;
+ int tail = 0;
int max_write_zeroes = MIN_NON_ZERO(bs->bl.max_write_zeroes,
BDRV_REQUEST_MAX_SECTORS);
+ if (bs->bl.write_zeroes_alignment) {
+ assert(is_power_of_2(bs->bl.write_zeroes_alignment));
+ head = sector_num & (bs->bl.write_zeroes_alignment - 1);
+ tail = (sector_num + nb_sectors) & (bs->bl.write_zeroes_alignment - 1);
+ max_write_zeroes &= ~(bs->bl.write_zeroes_alignment - 1);
+ }
while (nb_sectors > 0 && !ret) {
int num = nb_sectors;
/* Align request. Block drivers can expect the "bulk" of the request
- * to be aligned.
+ * to be aligned, and that unaligned requests do not cross cluster
+ * boundaries.
*/
- if (bs->bl.write_zeroes_alignment
- && num > bs->bl.write_zeroes_alignment) {
- if (sector_num % bs->bl.write_zeroes_alignment != 0) {
- /* Make a small request up to the first aligned sector. */
- num = bs->bl.write_zeroes_alignment;
- num -= sector_num % bs->bl.write_zeroes_alignment;
- } else if ((sector_num + num) % bs->bl.write_zeroes_alignment !=
0) {
- /* Shorten the request to the last aligned sector. num cannot
- * underflow because num > bs->bl.write_zeroes_alignment.
- */
- num -= (sector_num + num) % bs->bl.write_zeroes_alignment;
- }
+ if (head) {
+ /* Make a small request up to the first aligned sector. */
+ num = MIN(nb_sectors, bs->bl.write_zeroes_alignment - head);
+ head = 0;
+ } else if (tail && num > bs->bl.write_zeroes_alignment) {
+ /* Shorten the request to the last aligned sector. */
+ num -= tail;
}
/* limit request size */
diff --git a/tests/qemu-iotests/154.out b/tests/qemu-iotests/154.out
index 8946b73..b9d27c5 100644
--- a/tests/qemu-iotests/154.out
+++ b/tests/qemu-iotests/154.out
@@ -106,11 +106,14 @@ read 1024/1024 bytes at offset 67584
read 5120/5120 bytes at offset 68608
5 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
[{ "start": 0, "length": 32768, "depth": 1, "zero": true, "data": false},
-{ "start": 32768, "length": 8192, "depth": 0, "zero": false, "data": true,
"offset": 20480},
+{ "start": 32768, "length": 4096, "depth": 0, "zero": false, "data": true,
"offset": 20480},
+{ "start": 36864, "length": 4096, "depth": 0, "zero": true, "data": false},
{ "start": 40960, "length": 8192, "depth": 1, "zero": true, "data": false},
-{ "start": 49152, "length": 8192, "depth": 0, "zero": false, "data": true,
"offset": 28672},
+{ "start": 49152, "length": 4096, "depth": 0, "zero": false, "data": true,
"offset": 24576},
+{ "start": 53248, "length": 4096, "depth": 0, "zero": true, "data": false},
{ "start": 57344, "length": 8192, "depth": 1, "zero": true, "data": false},
-{ "start": 65536, "length": 8192, "depth": 0, "zero": false, "data": true,
"offset": 36864},
+{ "start": 65536, "length": 4096, "depth": 0, "zero": false, "data": true,
"offset": 28672},
+{ "start": 69632, "length": 4096, "depth": 0, "zero": true, "data": false},
{ "start": 73728, "length": 134144000, "depth": 1, "zero": true, "data":
false}]
== spanning two clusters, non-zero after request ==
@@ -145,11 +148,14 @@ read 7168/7168 bytes at offset 65536
read 1024/1024 bytes at offset 72704
1 KiB, X ops; XX:XX:XX.X (XXX YYY/sec and XXX ops/sec)
[{ "start": 0, "length": 32768, "depth": 1, "zero": true, "data": false},
-{ "start": 32768, "length": 8192, "depth": 0, "zero": false, "data": true,
"offset": 20480},
+{ "start": 32768, "length": 4096, "depth": 0, "zero": true, "data": false},
+{ "start": 36864, "length": 4096, "depth": 0, "zero": false, "data": true,
"offset": 20480},
{ "start": 40960, "length": 8192, "depth": 1, "zero": true, "data": false},
-{ "start": 49152, "length": 8192, "depth": 0, "zero": false, "data": true,
"offset": 28672},
+{ "start": 49152, "length": 4096, "depth": 0, "zero": true, "data": false},
+{ "start": 53248, "length": 4096, "depth": 0, "zero": false, "data": true,
"offset": 24576},
{ "start": 57344, "length": 8192, "depth": 1, "zero": true, "data": false},
-{ "start": 65536, "length": 8192, "depth": 0, "zero": false, "data": true,
"offset": 36864},
+{ "start": 65536, "length": 4096, "depth": 0, "zero": true, "data": false},
+{ "start": 69632, "length": 4096, "depth": 0, "zero": false, "data": true,
"offset": 28672},
{ "start": 73728, "length": 134144000, "depth": 1, "zero": true, "data":
false}]
== spanning two clusters, partially overwriting backing file ==
--
1.8.3.1
- [Qemu-devel] [PULL 00/31] Block layer patches, Kevin Wolf, 2016/06/08
- [Qemu-devel] [PULL 06/31] iscsi: Use block size as minimum zero/discard alignment, Kevin Wolf, 2016/06/08
- [Qemu-devel] [PULL 02/31] qcow2: simplify logic in qcow2_co_write_zeroes, Kevin Wolf, 2016/06/08
- [Qemu-devel] [PULL 07/31] block: Track write zero limits in bytes, Kevin Wolf, 2016/06/08
- [Qemu-devel] [PULL 08/31] block: Add .bdrv_co_pwrite_zeroes(), Kevin Wolf, 2016/06/08
- [Qemu-devel] [PULL 01/31] block: split write_zeroes always,
Kevin Wolf <=
- [Qemu-devel] [PULL 03/31] qcow2: add tracepoints for qcow2_co_write_zeroes, Kevin Wolf, 2016/06/08
- [Qemu-devel] [PULL 10/31] iscsi: Convert to bdrv_co_pwrite_zeroes(), Kevin Wolf, 2016/06/08
- [Qemu-devel] [PULL 11/31] qcow2: Convert to bdrv_co_pwrite_zeroes(), Kevin Wolf, 2016/06/08
- [Qemu-devel] [PULL 05/31] qcow2: Catch more unaligned write_zero into zero cluster, Kevin Wolf, 2016/06/08
- [Qemu-devel] [PULL 17/31] vmdk: Convert to bdrv_co_pwrite_zeroes(), Kevin Wolf, 2016/06/08
- [Qemu-devel] [PULL 19/31] migration/block: Convert load to BlockBackend, Kevin Wolf, 2016/06/08
- [Qemu-devel] [PULL 09/31] block: Switch bdrv_write_zeroes() to byte interface, Kevin Wolf, 2016/06/08
- [Qemu-devel] [PULL 21/31] block: assert that bs->request_alignment is a power of 2, Kevin Wolf, 2016/06/08
- [Qemu-devel] [PULL 15/31] raw-posix: Convert to bdrv_co_pwrite_zeroes(), Kevin Wolf, 2016/06/08
- [Qemu-devel] [PULL 18/31] block: Kill bdrv_co_write_zeroes(), Kevin Wolf, 2016/06/08