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

Lukas Larsson <>
Fri Aug 23 10:39:58 CEST 2013


Hello,

This looks great! I'll add it to our tests during the weekend and if 
nothing pops up merge it next week.

Lukas

On 22/08/13 20:58, Steve Vinoski wrote:
> I've amended the commit on my branch as described in my previous 
> message, please refetch.
>
> https://github.com/erlang/otp/pull/58
>
> thanks,
> --steve
>
>
>
> On Thu, Aug 22, 2013 at 12:55 PM, Steve Vinoski < 
> <mailto:>> wrote:
>
>     Hi Lukas,
>
>     Thanks for the feedback. After our IRC conversation today covering
>     the details of this issue, I agree it's clearer if this patch
>     doesn't introduce order dependencies between +S and +SP options or
>     introduce accumulated effects of multiple +SP options. I'll change
>     my branch to do the following:
>
>     * ensure that later +SP options on the command line completely
>     replace any previous +SP options, so there's no accumulated
>     effects between them (which implies "+SP 100:100" can undo any
>     previous +SP options)
>
>     * keep interactions between +S and +SP options, but remove
>     ordering dependencies, thus your example "+S 16:16 +SP 50:50 +S
>     16:16" would result in [8:8] as you've specified, as would both
>     "+SP 50:50 +S 16:16" and "+S 16:16 +SP 50:50"
>
>     * document and add tests for the already-existing feature that +S
>     0:0 undoes any prior +S options, resetting scheduler thread and
>     scheduler thread online counts to their defaults for the host
>
>     * document and add tests for the already-existing feature that
>     specifying negative numbers for +S results in the specified values
>     being subtracted from the scheduler thread and scheduler thread
>     online counts
>
>     I'll send another email when the branch is ready with these
>     changes. Any other concerns, please let me know.
>
>     thanks,
>     --steve
>
>
>
>     On Thu, Aug 22, 2013 at 10:11 AM, Lukas Larsson <
>     <mailto:>> wrote:
>
>         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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