lkml.org 
[lkml]   [2009]   [Dec]   [21]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: [RFC] CFQ group scheduling structure organization
On Mon, Dec 21, 2009 at 01:16:19PM +0100, Jens Axboe wrote:
> On Thu, Dec 17 2009, Munehiro Ikeda wrote:
> > Hello,
> >
> > Corrado Zoccolo wrote, on 12/17/2009 06:41 AM:
> >> Hi,
> >> On Wed, Dec 16, 2009 at 11:52 PM, Vivek Goyal<vgoyal@redhat.com> wrote:
> >>> Hi All,
> >>>
> >>> With some basic group scheduling support in CFQ, there are few questions
> >>> regarding how group structure should look like in CFQ.
> >>>
> >>> Currently, grouping looks as follows. A, and B are two cgroups created by
> >>> user.
> >>>
> >>> [snip]
> >>>
> >>> Proposal 4:
> >>> ==========
> >>> Treat task and group at same level. Currently groups are at top level and
> >>> at second level are tasks. View the whole hierarchy as follows.
> >>>
> >>>
> >>> service-tree
> >>> / | \ \
> >>> T1 T2 G1 G2
> >>>
> >>> Here T1 and T2 are two tasks in root group and G1 and G2 are two cgroups
> >>> created under root.
> >>>
> >>> In this kind of scheme, any RT task in root group will still be system
> >>> wide RT even if we create groups G1 and G2.
> >>>
> >>> So what are the issues?
> >>>
> >>> - I talked to few folks and everybody found this scheme not so intutive.
> >>> Their argument was that once I create a cgroup, say A, under root, then
> >>> bandwidth should be divided between "root" and "A" proportionate to
> >>> the weight.
> >>>
> >>> It is not very intutive that group is competing with all the tasks
> >>> running in root group. And disk share of newly created group will change
> >>> if more tasks fork in root group. So it is highly dynamic and not
> >>> static hence un-intutive.
> >
> > I agree it might be dynamic but I don't think it's un-intuitive.
> > I think it's reasonable that disk share of a group is
> > influenced by the number of tasks running in root group,
> > because the root group is shared by the tasks and groups from
> > the viewpoint of cgroup I/F, and they really share disk bandwidth.
>
> Agree, this is my preferred solution as well. There are definitely valid
> cases for both doing system wide RT and system wide idle, and there are
> definitely valid reasons for doing that inside a single group as well.
>

Thanks Jens. I will write a patch to implement above.

Vivek


\
 
 \ /
  Last update: 2009-12-21 15:45    [from the cache]
©2003-2011 Jasper Spaans