On 26.03.2014 10:16, Markus Armbruster wrote:
Peter Lieven <p...@kamp.de> writes:
this patch tries to optimize zero write requests
by automatically using bdrv_write_zeroes if it is
supported by the format.
this should significantly speed up file system initialization and
should speed zero write test used to test backend storage performance.
the difference can simply be tested by e.g.
dd if=/dev/zero of=/dev/vdX bs=1M
Got actual numbers? Preferably for some operation that matters to
users.
To give you a rough figure I have an iSCSI Storage for testing that
has an 1GBit connection. The above command gives about 110MB/s
with detect-zeroes=off and about 980MB/s with detect-zeroes=unmap.
Additionally I ran a test with v1 of the patch:
---8<---
I created a 60GB qcow2 container and formatted it with ext4. To immediately
show the difference
I disabled lazy inode table and lazy journal init (writing zero takes place
immediately then).
Timing without the patch:
time mkfs.ext4 -E lazy_itable_init=0,lazy_journal_init=0 /dev/vda
real 1m5.649s
user 0m0.416s
sys 0m3.148s
Timing with the patch:
time mkfs.ext4 -E lazy_itable_init=0,lazy_journal_init=0 /dev/vdX
real 0m1.228s
user 0m0.116s
sys 0m0.732s
Container Size after Format without the patch: 1150615552 Byte (1097.3MB)
Container Size after Format with the patch: 24645632 Byte (23.5MB)
--->8---
Without the patch means detect-zeroes=off (default) and with the patch means
detect-zeroes=unmap.
BR,
Peter
