Messages in this thread |  | | | Date | Tue, 29 May 2012 14:18:39 +0200 | | From | Juri Lelli <> | | Subject | Re: [PATCH 13/15] sched: add bandwidth management for sched_dl. |
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On 05/29/2012 11:58 AM, Peter Zijlstra wrote: > On Sat, 2012-05-26 at 13:07 +0200, Juri Lelli wrote: >> Hi, >> >> On 05/25/2012 12:38 PM, Peter Zijlstra wrote: >>> On Wed, 2012-05-23 at 23:42 +0200, Juri Lelli wrote: >>>> +/* >>>> + * Coupling of -dl and -rt bandwidth. >>>> + * >>>> + * Here we check, while setting the system wide bandwidth available >>>> + * for -dl tasks and groups, if the new values are consistent with >>>> + * the system settings for the bandwidth available to -rt entities. >>>> + * >>>> + * IOW, we want to enforce that >>>> + * >>>> + * rt_bandwidth + dl_bandwidth<= 100% >>>> + * >>>> + * is always true. >>>> + */ >>> >>> I was thinking we could do it the other way around, have have >>> dl_bandwidth included in rt_bandwidth. >>> >> >> If I understand correctly, you are proposing to treat -dl tasks as a >> special case of "real-time" tasks. Then we could reserve some bw to >> "real-time" (rt_bandwidth cap) activities and give a piece of this >> bw to -dl tasks (what remains is for -rt tasks). This is in principle >> nice and useful, but I'm not quite sure that this is the right point >> to achieve this logical behavior. >> I mean, -dl and -rt tasks are separately treated, so it is probably >> cleaner to manage their knobs separately. They have to coexist rather >> than be considered one a sub-case of the other. A better way to go >> for a common cap for them is probably the (long-term) hierarchical >> scheduling mechanism. >> >> So, I would prefer to keep the interface as is for now, but I can also >> completely misunderstood your thoughts :-P. > > The thing is, keeping it separate makes for an impossible configuration > scenario. Esp. once we enable !root usage. The proposed 5% is very > limiting and regular users won't have sufficient privilege to change it. >
Ok, now I understand your point better, and I agree that 5% is hardly usable for !root users. However, I also think this is probably more a system admin problem. I mean, a sys admin that wants his users to play with -deadline scheduling should have thought how to properly set up his system, and the fact that something must be configured by hand to give users a usable system is generally not a so bad idea.
> Also lowering FIFO/RR by default isn't a real option since people expect > that to get all time already (however silly that expectation is). >
I agree. Don't want to spoil users expectations :-).
Thanks and regards,
- Juri
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