Messages in this thread |  | | | Date | Tue, 08 Sep 2009 12:01:19 +0900 (JST) | | Subject | Re: Regarding dm-ioband tests | | From | Ryo Tsuruta <> |
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Hi Rik,
Rik van Riel <riel@redhat.com> wrote: > Ryo Tsuruta wrote: > > > However, if you want to get fairness in a case like this, a new > > bandwidth control policy which controls accurately according to > > assigned weights can be added to dm-ioband. > > Are you saying that dm-ioband is purposely unfair, > until a certain load level is reached?
Not unfair, dm-ioband(weight policy) is intentionally designed to use bandwidth efficiently, weight policy tries to give spare bandwidth of inactive groups to active groups.
> > We regarded reducing throughput loss rather than reducing duration > > as the design of dm-ioband. Of course, it is possible to make a new > > policy which reduces duration. > > ... while also reducing overall system throughput > by design?
I think it reduces system throughput compared to the current implementation, because it causes more overhead to do fine grained control.
> Why are you even bothering to submit this to the > linux-kernel mailing list, when there is a codebase > available that has no throughput or fairness regressions? > (Vivek's io scheduler based io controler)
I think there are some advantages to dm-ioband. That's why I post dm-ioband to the mailing list.
- dm-ioband supports not only proportional weight policy but also rate limiting policy. Besides, new policies can be added to dm-ioband if a user wants to control bandwidth by his or her own policy. - The dm-ioband driver can be replaced without stopping the system by using device-mapper's facility. It's easy to maintain. - dm-ioband can use without cgroup. (I remember Vivek said it's not an advantage.)
Thanks, Ryo Tsuruta
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