Messages in this thread | | | From | "Davide Libenzi" <> | Subject | Re: Interesting analysis of linux kernel threading by IBM | Date | Thu, 20 Jan 2000 14:33:30 +0100 |
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Hi Horst,
Thursday, January 20, 2000 1:51 PM Horst von Brand <vonbrand@pincoya.inf.utfsm.cl> write : > > my patch has great performance ( 80% with 300 tasks ) with a lot of tasks > > and low overhead ( 1.5% with 2 tasks ). > > And my patch has 0.00 optimizations about CPU fetches and Co. > > IMVHO 1-1.5 % of overhead is a price the we can afford given the performace > > with many tasks. > > My patch equals the current implementation with 8 tasks. > > So it is a net loss. This machine here (a personal workstation) has > typically 1 to 3 running tasks. > > Hondreds of tasks is just not a typical (perhaps even realistic) > workload.
under a normal switching workload You get the same performance ( perhaps less than 1% ) but when the game become hard ( in a task-switching sense ) You get a logarithmic response of the scheduler as function of the number of processes ( now is linear ). The numbers are these :
300 running processes ( I say running not in runqueue ) 12 up to 35 in runqueue I get an 83% performance improvement
2 running processes ( that switch at the same rate of 300 ) I get 11% up to 15% performance loss
But the fact is that normally 2 tasks switches at a very lower factor then 300. The probability that a task get scheduled or require a schedule() call. I We apply a liner low we get :
15 * 2 / 300 = 0.1 % loss
in a real 2 tasks workload. IMVHO we can sustain this loss given the results at higher switching workloads.
Cheers, Davide.
-- Debian, the freedom in freedom.
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