Re: [PATCH] UBI: Add volume read and write statistics

["Per Förlin" <per.forlin@axis.com>]

> ________________________________________
> From: Richard Weinberger <richard@nod.at>
> Sent: Tuesday, July 17, 2018 5:10 PM
> To: Steve deRosier
> Cc: Per Förlin; linux-mtd@lists.infradead.org; Artem Bityutskiy
> Subject: Re: [PATCH] UBI: Add volume read and write statistics
> 
> Am Dienstag, 17. Juli 2018, 17:06:12 CEST schrieb Steve deRosier:
> > > > While having a cup of coffee I thought more about this.
> > > > Actually both, MTD and UBI makes sense.
> > > > The most important issue is that you integrate it with the existing diskstats.
> > > > So instead of having our own interface feeding MTD/UBI stats into diskstats
> > > > would be nice. Did you look into that? I'm not sure how much work this would be.
> > > > That way users can use existing tools such as iostat...
> > > I actually started out looking for the information under diskstats,
> > > then I learned it's only for block devices. I took a quick glance at
> > > it before I went for the sys implementation instead. diskstats is
> > > separated from the MTD and UBI stuff and I don't know if one can make a
> > > connection to MTD/UBI somehow. I will take a closer look at this.
> >
> > Perhaps it was "only for block devices" because no one ever
> > implemented the necessary hooks in MTD or UBI?  I don't know the
> > history, nor the information you found, just making a stab in the
> > dark.
> >
> > If UBI and/or MTD can provide the statistics that diskstats needs in a
> > interpretation that makes sense, why not go that way?
> 
> Yeah, that's what I have in mind. Maybe we can easily teach diskstats
> about MTD.
Now I got the chance to look at this again. It's not as bad as I thought.
The diskstats simply takes the block class and iterate over all devices.
For each device statistics are printed out.
It should be possible to do the same for the MTD class and the UBI class.
So far I haven't tested anything just reading code.
Then it's a matter of taste. Is MTD and UBI stats welcome in genhd.c?

I will try to find time the coming days or so to make a prove of concept
implementation to get a better idea of how big the change would be.