[linux-lvm] heat map

[Alasdair G Kergon]

On Mon, Jun 24, 2013 at 12:04:00AM -0700, matthew patton wrote:
> If some older man pages are to be believed there once was a capability
> to keep a heat map of busy extents. Is there a way to revive that
> capability? I expect "last I/O within 30 seconds, 5 minute, 15minute" is
> probably sufficient for most uses as well as summary counters along the
> same lines.
 
Mikulas is developing a replacement here:
  http://people.redhat.com/~mpatocka/patches/kernel/dm-statistics/

Documentation appears at the end of the kernel patch.

If you want to try it out at the moment, you'll need this patch first I think:
  http://people.redhat.com/agk/patches/linux/editing/dm-optimize-use-SRCU-and-RCU.patch

Alasdair