Messages in this thread | | | Date | Wed, 12 Apr 2006 12:28:56 +0400 | From | Kirill Korotaev <> | Subject | Re: [Devel] Re: [RFC] Virtualization steps |
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Sam,
> Ok, I'll call those three VPSes fast, faster and fastest. > > "fast" : fill rate 1, interval 3 > "faster" : fill rate 2, interval 3 > "fastest" : fill rate 3, interval 3 > > That all adds up to a fill rate of 6 with an interval of 3, but that is > right because with two processors you have 2 tokens to allocate per > jiffie. Also set the bucket size to something of the order of HZ. > > You can watch the processes within each vserver's priority jump up and > down with `vtop' during testing. Also you should be able to watch the > vserver's bucket fill and empty in /proc/virtual/XXX/sched (IIRC) > > I mentioned this earlier, but for the sake of the archives I'll repeat - > if you are running with any of the buckets on empty, the scheduler is > imbalanced and therefore not going to provide the exact distribution you > asked for. > > However with a single busy loop in each vserver I'd expect the above to > yield roughly 100% for fastest, 66% for faster and 33% for fast, within > 5 seconds or so of starting those processes (assuming you set a bucket > size of HZ).
Sam, what we observe is the situation, when Linux cpu scheduler spreads 2 tasks on 1st CPU and 1 task on the 2nd CPU. Std linux scheduler doesn't do any rebalancing after that, so no plays with tokens make the spread to be 3:2:1, since the lowest priority process gets a full 2nd CPU (100% instead of 33% of CPU).
Where is my mistake? Can you provide a configuration where we could test or the instuctions on how to avoid this?
Thanks, Kirill
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