[erlang-questions] schedulers binding error

Rickard Green <>
Sat Mar 6 02:11:27 CET 2010


2010/3/5 Angel <>:
> Hello!
>
> after compiling erlang on a itanium numa machine i cant use +sbt flag
>
> No cpu topology is detected, after asking here and playing a bit I got:
>
> erl +sct L0c0p0N0:L1c1p1N0:L2c2p2N1:L3c3p3N1:L4c4p4N2:L5c5p5N2:L6c6p6N3:L7c7p7N3:L8c8p8N4:L9c9p9N4:L10c10p10N5:L11c11p11N5
>
> that get me 12 procs over 6 numa nodes, good!!
>
> but playing a bit with a lot of processes showed me that erlang was not fully use all proccesors
>
> So i relayed to use +sbt to see how binding changes cpu stats....
>
> but erlang refuses to use any bindings:
>
>
>  otp_src_R13B04]$ erl +scyt ... +sbt u  +A6
> setting scheduler bind type 'u' failed: not supported
> ....
>
>
>  otp_src_R13B04]$ erl +scyt ... +sbt nnps  +A6
> setting scheduler bind type 'nnps' failed: not supported
> ....
>
> My kernel is 2.4.21-sgi306rp12  Its too old for this!!! isn't it?
>
>

Yes. Schedulers are bound using sched_setaffinity() which appeared in
kernel 2.5.8 according to the man page.

Regards,
Rickard Green, Erlang/OTP, Ericsson AB.


> A/ngel
>
>
> Most people know C is not so high level....
>                ...Everybody else just got assembler overdose
>
>
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