Re: [Xen-devel] dm-band: The I/O bandwidth controller: Performance Report

Hi,

you mean that you run 128 processes on each user-device pairs?  Namely,
I guess that

  user1: 128 processes on sdb5,
  user2: 128 processes on sdb5,
  another: 128 processes on sdb5,
  user2: 128 processes on sdb6.

"User-device pairs" means "band groups", right?
What I actually did is the followings:

  user1: 128 processes on sdb5,
  user2: 128 processes on sdb5,
  user3: 128 processes on sdb5,
  user4: 128 processes on sdb6.

The second preliminary studies might be:
- What if you use a different I/O size on each device (or device-user pair)?
- What if you use a different number of processes on each device (or
device-user pair)?

There are other ideas of controlling bandwidth, limiting bytes-per-sec,
latency time or something. I think it is possible to implement it if 
a lot of people really require it. I feel there wouldn't be a single
correct answer for this issue. Posting good ideas how it should work
and submitting patches for it are also welcome.

And my impression is that it's natural dm-band is in device-mapper,
separated from I/O scheduler.  Because bandwidth control and I/O
scheduling are two different things, it may be simpler that they are
implemented in different layers.

I would like to know how dm-band works on various configurations on
various type of hardware. I'll try running dm-band on with other
configurations. Any reports or impressions of dm-band on your machines
are also welcome.

Thanks,
Ryo Tsuruta