[erlang-patches] patch to add option to set schedulers by percentage

Lukas Larsson <>
Thu Aug 22 16:11:54 CEST 2013


Hello Steve,

Have you given any thoughts on what should happen if you chain multiple 
+SP commands? i.e.

erl +S 16:16 +SP 50:50 +SP 50:50

Our view right now is that this should give [8:8] and not [4:4] as it 
currently does in the patch.

Related to this we also do not think that the order to +S vs +SP 
commands should matter. i.e.

erl +S 16:16 +SP 50:50 +S 16:16

should give [8:8] and not [16:16].

What do you think? These things are for sure odd cases to think about, 
but if it is possible someone will for sure do it....

Lukas

On 21/08/13 15:45, Steve Vinoski wrote:
> For applications where measurements show enhanced performance from the 
> use of a non-default number of emulator scheduler threads, having to 
> accurately set the right number of scheduler threads across multiple 
> hosts each with different numbers of logical processors is difficult 
> because the erl +S option requires absolute numbers of scheduler 
> threads and scheduler threads online to be specified.
>
> To address this issue, this patch adds a +SP option to erl, similar to 
> the existing +S option but allowing the number of scheduler threads 
> and scheduler threads online to be set as percentages of logical 
> processors configured and logical processors available, respectively. 
> For example, "+SP 50:25" sets the number of scheduler threads to 50% 
> of the logical processors configured, and the number of scheduler 
> threads online to 25% of the logical processors available.
>
> https://github.com/erlang/otp/pull/58
>
> --steve
>
>
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> 
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