Messages in this thread | | | Date | Mon, 10 Nov 2008 08:44:07 -0500 | From | Vivek Goyal <> | Subject | Re: [patch 1/4] io controller: documentation |
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On Mon, Nov 10, 2008 at 10:48:54AM +0800, Li Zefan wrote: > Hi, Vivek > > Thanks for your work. :) > > A question below. > > > +For example, assume there are two cgroups A and B with weights 1024 and 2048 > > +in the system. Tasks in two cgroups A and B are doing IO to two disks sda and > > +sdb in the system. A user has enabled IO control on both sda and sdb. Now on > > +both sda and sdb, tasks in cgroup B will get to use 2/3 of disk BW and > > +tasks in cgroup A will get to use 1/3 of disk bandwidth, only in case of > > +contention. If tasks in any of the groups stop doing IO to a particular disk, > > +task in other group will get to use full disk BW for that duration. > > + > > So in this example, I can't assign 1/3 of sda's disk BW while 2/3 of sdb's > disk BW to A. Am I right?
Hi,
Yes you are right. Currently policies are global and not per disk. So in above example, cgroup A will get 1/3 of disk BW both on sda and sdb. And one can not configure in such a manner so that A gets 1/3 of BW on sda and 2/3 of BW on sdb.
I think assigning cgroup weights per disk should be doable but personally I think it makes configuration complex and I am not sure if it really a very useful feature.
Thanks Vivek
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