On Fri, Apr 17, 2009 at 09:56:31AM +0800, Li Zefan wrote: > KAMEZAWA Hiroyuki wrote: > > On Tue, 14 Apr 2009 22:21:12 +0200 > > Andrea Righi <righi.andrea@xxxxxxxxx> wrote: > > > >> +Example: > >> +* Create an association between an io-throttle group and a bio-cgroup group > >> + with "bio" and "blockio" subsystems mounted in different mount points: > >> + # mount -t cgroup -o bio bio-cgroup /mnt/bio-cgroup/ > >> + # cd /mnt/bio-cgroup/ > >> + # mkdir bio-grp > >> + # cat bio-grp/bio.id > >> + 1 > >> + # mount -t cgroup -o blockio blockio /mnt/io-throttle > >> + # cd /mnt/io-throttle > >> + # mkdir foo > >> + # echo 1 > foo/blockio.bio_id > > > > Why do we need multiple cgroups at once to track I/O ? > > Seems complicated to me. > > > > IIUC, it also disallows other subsystems to be binded with blockio subsys: > # mount -t cgroup -o blockio cpuset xxx /mnt > (failed) > > and if a task is moved from cg1(id=1) to cg2(id=2) in bio subsys, this task > will be moved from CG1(id=1) to CG2(id=2) automatically in blockio subsys. > > All these are odd, unexpected, complex and bug-prone I think.. Implementing bio-cgroup functionality as pure infrastructure framework instead of a cgroup subsystem would remove all this oddity and complexity. For example, the actual functionality that I need for the io-throttle controller is just an interface to set and get the cgroup owner of a page. I think it should be the same also for other potential users of bio-cgroup. So, what about implementing the bio-cgroup functionality as cgroup "page tracking" infrastructure and provide the following interfaces: /* * Encode the cgrp->css.id in page_group->flags */ void set_cgroup_page_owner(struct page *page, struct cgroup *cgrp); /* * Returns the cgroup owner of a page, decoding the cgroup id from * page_cgroup->flags. */ struct cgroup *get_cgroup_page_owner(struct page *page); This also wouldn't increase the size of page_cgroup because we can encode the cgroup id in the unused bits of page_cgroup->flags, as originally suggested by Kame. And I think it could be used also by dm-ioband, even if it's not a cgroup-based subsystem... but I may be wrong. Ryo what's your opinion? -Andrea _______________________________________________ Containers mailing list Containers@xxxxxxxxxxxxxxxxxxxxxxxxxx https://lists.linux-foundation.org/mailman/listinfo/containers