Hello Joe,
I updated to the latest kernel from Ubuntu mainline (4.2.0-040200rc1)
and will rerun the same fio command over the night. Currently it shows
the same behaviour. The fio command i use is
fio --name=test --filename=/dev/mapper/dmcache --rw=randwrite
--filesize=16G --bs=64k --ioengine=libaio --direct=1 --iodepth=1000
After 4 runs, the status for the device mapper looks like this:
dmcache: 0 6442450943 cache 8 6029/4161600 512 2283/2913051 1517 119
25120 1294780 0 2283 1484 1 writeback 2 migration_threshold 2048 smq 0 rw
Regards
Christoph
Am 08.07.2015 um 16:48 schrieb Joe Thornber:
On Wed, Jul 08, 2015 at 11:03:42AM +0200, Christoph Nelles wrote:
Hi,
Can the dm-cache writeback cache buffer direct IO or goes direct IO
always immediately to the origin device?
Yes, the device mapper layer knows nothing about direct IO vs page
cache IO.
I am currently performing tests and see that random direct write IO
never hits the cache, even after overwriting the same region over
and over.
Could you try with the latest kernels and the new smq policy please?
- Joe
--
dm-devel mailing list
dm-devel@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/dm-devel
--
dm-devel mailing list
dm-devel@xxxxxxxxxx
https://www.redhat.com/mailman/listinfo/dm-devel
