[dm-devel] [PATCH 3/7] dm: add reserved_bio_based_ios module parameter

Mikulas Patocka mpatocka at redhat.com
Thu Sep 12 23:17:27 UTC 2013



On Thu, 12 Sep 2013, Mike Snitzer wrote:

> On Thu, Sep 12 2013 at  6:47pm -0400,
> Mikulas Patocka <mpatocka at redhat.com> wrote:
> 
> > We don't need this. bio-based i/o should be fine with a small mempool, 
> > there is no need to make it tunable.
> 
> I'd like to get Frank's insight here.  He clearly had an interest in
> tuning bio-based also.  While 16 shouldn't really hurt it could still be
> artifically high.  I'm not opposed to exposing a sane default but
> allowing other to experiemnt (in production workloads) with smaller
> values that still enable forward progress should memory get exhausted.
> 
> Mike

I would do it this way: if Frank gets a measurable improvement in memory 
consumption when the values is dropped from 16 to a lower number (4 or 
maybe 1), then I would drop the value by default (don't make it tunable, 
drop it for all users).

If there is no improvement when the value is lowered, I'd leave it as it 
is, on 16.

Mikulas




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