Re: [dm-devel] convert dm-thin to use dm-bufio

[Alasdair G Kergon <agk redhat com>]

On Fri, Aug 19, 2011 at 09:49:21AM -0400, Mike Snitzer wrote:
> On Fri, Aug 19 2011 at  6:22am -0400,
> Joe Thornber <thornber redhat com> wrote:
> > Assuming agk doesn't decide to switch over to a kmemcache.  Remember
> > bm used to allocate via kmalloc or pages like bufio.
> Indeed.
  
The basic requirement is to know accurately how much memory is being used
by the module (and ultimately per-pool device) as I can imagine cases 
where it's using a significant proportion of the system's memory.

I doubt kmemcache would be a satisfactory solution for bufio, but there
are other ways to meet this requirement, such as exporting this
information in /sys.  Initally just a global figure for the module, but
evenutally reported per-device (with dm-core support and new target
callbacks).

Alasdair