Re: bcache kernel 3.10 wrong bypassed values

[Kent Overstreet <kmo-PEzghdH756F8UrSeD/g0lQ@public.gmane.org>]

On Thu, Jul 04, 2013 at 10:13:20AM +0200, Stefan Priebe - Profihost AG wrote:
> Hello list,
> 
> while testing bcache i noticed that while writing a big 48GB file the
> sequential cutoff works fine i see only I/O on the disk but not on the
> cache. I thought i would afterwards see a bypassed value of around 48GB
> but it is only 1.2GB.
> 
> Is this expected? Is bcache in kernel 3.10 stable for production usage?

That sounds like a bug, but bcache in 3.10 certainly should be stable
for production usage.

There can be some weirdness due to the way the stats work, there's a ~13
second update interval (and also the intermediate counters are 32 bit
ints so if you manage to wrap that in 13 seconds you'll lose counts, but
it's counting sectors so I doubt that happened here).

Does that sound like it might explain what you were seeing, or do you
think there's something else going on?