Messages in this thread |  | | | Date | Thu, 26 Feb 2009 14:18:15 +0530 | | From | Dhaval Giani <> | | Subject | Re: [RFC PATCH 1/2] New cgroup subsystem API (->initialize()) |
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On Thu, Feb 26, 2009 at 01:22:59PM +0530, Bharata B Rao wrote: > On Thu, Feb 26, 2009 at 10:55:54AM +0800, Li Zefan wrote: > > Bharata B Rao wrote: > > > From: Balaji Rao <balajirrao@gmail.com> > > > > > > cgroup: Add ->initialize() to cgroup_subsys structure > > > > > > Some cgroup subsystems (like cpu controller) would need subsystem > > > specific initialization. Such subsystems can define ->initialize() > > > which gets called during cgroup_init() (and not cgroup_init_early()). > > > > > > > I think it's better to avoid adding this. > > > > It would be best if we can add a hook to initialize init_task_group.stat where > > kmalloc is available but acount_xxx_time() hasn't been called. Otherwise, we > > have to check (tg->stat == NULL) in account_task_group_time(), then why not add > > a hook in smp_init_smp() to do initialization? > > account_xxx_time() is called from scheduler ticks and AFAICS they end up > getting called much before kmalloc is available. In any case, I would think > any hook to just initialize stats for init_task_group would be > very very (cpu controller) subsytem specific. Isn't that bad ? > > Another solution I see which can prevent all this is not to collect > stats for init_task_group at all with the understanding that system wide > stime/utime accounting (which is already present) is essentially the > accounting for init_task_group because init_task_group comprises of all > the tasks in the system. But this would necessiate us to make collection > of cpu controller stats hierarchial. This was one of the questions I asked > in my 0/2 thread. Shouldn't we be doing hierarchial accounting for > cpu controller ? >
I believe hierarchical accounting is natural. Since the CPU controller divides its bandwidth as per hierarchy, it makes sense for the accounting to also be hierarchical. I guess this is a reasonable compromise. But how do you still check if the group you are accounting for is the root group or not? (Unless I am missing something obvious)
thanks, -- regards, Dhaval
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