Hi Coly

Thanks for your quick reply. I’ve already solved this problem by updating kernel version to 3.18.63. So I think there must be a bug in old bcache code of 3.10 kernel version.

在 2017年8月9日，下午8:58，Coly Li [off-list ref] 写道：

On 2017/8/9 下午3:09, cgxu wrote:

quoted

HI

I make bcache device using NVMe ssd device as cache and 4T SATA disk as backing device.

I found write performance is extremely poor in writeback cache_mode but raw ssd has very high performance.

I monitored io workload using iostat for a while, so I'm sure it really worked in writeback mode.

can anyone explain this problem？ Is there any compatible issue with special hardware?

Could you please to provide exact steps to reproduce the poor
performance situation ? When back ground writeback and garbage
collection is performing, front end regular I/O (especially write I/O)
performance is expected to downgrade.


-- 
Coly Li