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>
diff --git a/hmp.c b/hmp.c
index 5c4d612..ff506f3 100644
--- a/hmp.c
+++ b/hmp.c
@@ -341,6 +341,11 @@
info->value->inserted->backing_file_depth);
}
+ if (info->value->inserted->detect_zeroes != BLOCKDEV_DETECT_ZEROES_OPTIONS_OFF) {
+ monitor_printf(mon, " Detect zeroes: %s\n",
+ BlockdevDetectZeroesOptions_lookup[info->value->inserted->detect_zeroes]);
+ }
+
if (info->value->inserted->bps
|| info->value->inserted->bps_rd
|| info->value->inserted->bps_wr
