** Changed in: linux (Ubuntu)
Importance: Undecided => Medium
** Tags added: kernel-da-key
** Also affects: linux (Ubuntu Bionic)
Importance: Undecided
Status: New
** Changed in: linux (Ubuntu Bionic)
Status: New => Triaged
** Changed in: linux (Ubuntu)
Status: Confir
I confirmed that the underlying block devices (SAS, NVME) perform the same
on the 4.4 and 4.15 kernels. Roughly 170 IOP/s direct to the SAS device
and 570 IOP/s direct to the bcache infront of the SAS device. The block
scheduler has no effect, due to the use of O_DIRECT.
Can you collect the following:
Backing device baseline (it's possible the underlying disks regressed
instead of the bcache layer). the same fio randrw test against the
underlying backing device with bcache disabled
And with bcache enabled on both setups before and after tuning:
1) grep -r . /sys
Script used to tune bcache devices
** Attachment added: "tune-bcache"
https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1806015/+attachment/5217652/+files/tune-bcache
** Description changed:
Whilst diagnosing a disk performance issue on our QA cloud, I did some
performance testing of
