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authorPeter Lieven <pl@kamp.de>2014-05-18 00:58:19 +0200
committerKevin Wolf <kwolf@redhat.com>2014-05-19 13:42:27 +0200
commit465bee1da82e43f18d10c43cc7566d0284ad13a9 (patch)
treec98c26268e8f10a77bfc39abb72f72f8c7ac9ee8 /qmp-commands.hx
parent82a402e99f3f8c6177528ad6d561bf07ff6ee606 (diff)
downloadqemu-arm-465bee1da82e43f18d10c43cc7566d0284ad13a9.tar.gz
block: optimize zero writes with bdrv_write_zeroes
this patch tries to optimize zero write requests by automatically using bdrv_write_zeroes if it is supported by the format. This significantly speeds up file system initialization and should speed zero write test used to test backend storage performance. I ran the following 2 tests on my internal SSD with a 50G QCOW2 container and on an attached iSCSI storage. a) mkfs.ext4 -E lazy_itable_init=0,lazy_journal_init=0 /dev/vdX QCOW2 [off] [on] [unmap] ----- runtime: 14secs 1.1secs 1.1secs filesize: 937M 18M 18M iSCSI [off] [on] [unmap] ---- runtime: 9.3s 0.9s 0.9s b) dd if=/dev/zero of=/dev/vdX bs=1M oflag=direct QCOW2 [off] [on] [unmap] ----- runtime: 246secs 18secs 18secs filesize: 51G 192K 192K throughput: 203M/s 2.3G/s 2.3G/s iSCSI* [off] [on] [unmap] ---- runtime: 8mins 45secs 33secs throughput: 106M/s 1.2G/s 1.6G/s allocated: 100% 100% 0% * The storage was connected via an 1Gbit interface. It seems to internally handle writing zeroes via WRITESAME16 very fast. Signed-off-by: Peter Lieven <pl@kamp.de> Signed-off-by: Kevin Wolf <kwolf@redhat.com>
Diffstat (limited to 'qmp-commands.hx')
-rw-r--r--qmp-commands.hx3
1 files changed, 3 insertions, 0 deletions
diff --git a/qmp-commands.hx b/qmp-commands.hx
index cae890ee5d..2c53c1ba2e 100644
--- a/qmp-commands.hx
+++ b/qmp-commands.hx
@@ -2032,6 +2032,8 @@ Each json-object contain the following:
- "iops_rd_max": read I/O operations max (json-int)
- "iops_wr_max": write I/O operations max (json-int)
- "iops_size": I/O size when limiting by iops (json-int)
+ - "detect_zeroes": detect and optimize zero writing (json-string)
+ - Possible values: "off", "on", "unmap"
- "image": the detail of the image, it is a json-object containing
the following:
- "filename": image file name (json-string)
@@ -2108,6 +2110,7 @@ Example:
"iops_rd_max": 0,
"iops_wr_max": 0,
"iops_size": 0,
+ "detect_zeroes": "on",
"image":{
"filename":"disks/test.qcow2",
"format":"qcow2",