Messages in this thread | | | Date | Sat, 03 Jun 2006 00:28:26 +0530 | From | Balbir Singh <> | Subject | Re: [ckrm-tech] [RFC 3/5] sched: Add CPU rate hard caps |
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Peter Williams wrote: > Balbir Singh wrote: > >>Peter Williams wrote: >><snip> >> >>>>>But you don't need something as complex as CKRM either. This capping >>>> >>>>All CKRM^W Resource Groups does is to group unrelated/related tasks to a >>>>group and apply resource limits. >>>> >>>> >>>>>functionality coupled with (the lamented) PAGG patches (should have >>>>>been called TAGG for "task aggregation" instead of PAGG for "process >>>>>aggregation") would allow you to implement a kernel module that >>>>>could apply caps to arbitrary groups of tasks. >>>> >>>>I do not follow how PAGG + this cap feature can be used to put cap of >>>>related/unrelated tasks. Can you provide little more explanation, >>>>please. >>> >>> >>>I would have thought it was fairly obvious. PAGG supplies the task >>>aggregation mechanism, these patches provide per task caps and all >>>that's needed is the code that marries the two. >>> >> >>The problem is that with per-task caps, if I have a resource group A >>and I want to limit it to 10%, I need to limit each task in resource >>group A to 10% (which makes resource groups not so useful). Is my >>understanding correct? > > > Well the general idea is correct but your maths is wrong. You'd have to > give each of them a cap somewhere between 10% and 10% divided by the > number of tasks in group A. Exactly where in that range would vary > depending on the CPU demand of each task and would need to be adjusted > dynamically (unless they were very boring tasks whose demands were > constant over time). >
Hmm.. I thought my math was reasonable (but there is always so much to learn) From your formula, if I have 1 task in group A, I need to provide it with a cap of b/w 10 to 11%. For two tasks, I need to give them b/w 10 to 10.5%. If I have a hundred, it needs to be b/w 10% and 10.01%
> >>Is there a way to distribute the group limit >>across tasks in the resource group? > > > Not as part of this patch but it could be done from outside the > scheduler either in the kernel or in user space. > > >>>>Also, i do not think it can provide guarantees to that group of tasks. >>>>can it ? >>> >>> >>>It could do that by manipulating nice which is already available in >>>the kernel. >>> >>>I.e. these patches plus improved statistics (which are coming, I hope) >>>together with the existing policy controls provide all that is >>>necessary to do comprehensive CPU resource control. If there is an >>>efficient way to get the statistics out to user space (also coming, I >>>hope) this control could be exercised from user space. >> >>Could you please provide me with a link to the new improved statistics. > > > No. Read LKML and you'll know as much as I do. > > >>What do the new statistics contain - any heads up on them? > > > There're several contenders (including some from IBM) that periodically > post patches to LKML. That's where I'm aware of them from. As I say, > I'm hoping that they get together and come up with something generally > useful (as opposed to just meeting each contenders needs). I may be > being overly optimistic but you never know.
Yes, thats the whole point of the discussion and everybody is free to participate.
> > Peter
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Balbir Singh, Linux Technology Center, IBM Software Labs - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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