Re: Bcache stuck at writeback of a key, consuming 100% CPU, not possible to detach

[Vojtech Pavlik <vojtech@suse.cz>]

On Mon, Aug 31, 2015 at 07:04:29AM -0800, Kent Overstreet wrote:

> I suspect there's two different bugs here.
> 
>  - I'm starting to suspect there's a bug in the dirty data accounting, and it's
>    getting out of sync - i.e. reading 2.8 GB or whatever when it's actually 0.
>    that would explain it spinning when there actually isn't any work for it to
>    do.
> 
>  - with a large enough amount of data, the 30 second writeback_delay may be
>    insufficient; if it takes longer than that just to scan the entire keyspace
>    it'll never get a chance to sleep. try bumping writeback_delay up and see if
>    that helps.
> 
>    the ratelimiting on scanning for dirty data needs to be changed to something
>    more sophisticated, the existing fixed delay is problematic.

Is there any difference regarding writeback problems between using 4.1.6
and your bcache-dev git branch?

It may take a bit of effort, but I should be able to get bcache-dev
installed on my system.

-- 
Vojtech Pavlik
Director SuSE Labs