[erlang-questions] How to test multi-pollset?

[pablo platt]

Master with multi poll-sets is running on my dev machine without errors so
far.

What's the difference between polling threads and poll-sets (+IOt  and +IOp
)?
How do I know if I should increase the number of polling threads or
poll-sets?
I'm using a 8 or 16 vCPUs machine (vCPU =  hyper-threads) running Ubuntu
16.04.

I've measured with msacc as the docs [1] recommends on 1 vCPU machine.
Each gen_udp receiving 100 UDP packets per second increase the 'poll' row
load by about 0.05%.
Adding several gen_udp that send 100 UDP packets per second almost doesn't
affect the load.
Is it expected that gen_udp receiving packets has high load but gen_udp
sending packets very low load?

How can I compare master with multiple poll-sets with erlang/otp 20?
msacc on otp 20 doesn't have stats about poll.

msacc docs [2] don't show example output of poll load. Maybe not that
important.

[1] https://github.com/erlang/otp/blob/master/erts/doc/src/erl.xml
[2]
https://github.com/erlang/otp/blob/master/lib/runtime_tools/doc/src/msacc.xml


On Mon, Jan 29, 2018 at 11:19 AM, pablo platt <pablo.platt@REDACTED> wrote:

> It's great to see all the hard work invested in performance in master.
> Thanks.
>
> On Mon, Jan 29, 2018 at 10:49 AM, Lukas Larsson <lukas@REDACTED> wrote:
>
>> Hello,
>>
>> On Mon, Jan 29, 2018 at 9:22 AM, pablo platt <pablo.platt@REDACTED>
>> wrote:
>>
>>> Hi,
>>>
>>> What is the expected effect of the multi-pollset PR [1] on a UDP socket
>>> on the sender/receiver side?
>>> My use case is a media server with several broadcaster and many viewers.
>>> Each stream use 1Mbps (aprox 100 * 1500 bytes packets per second).
>>> Should I expect improvement when gen_udp is sending packets, receiving
>>> packets or both?
>>>
>>
>> Yes, I believe that you will see an improvement. It depends on what type
>> of HW that you are running on, typically the more logical cpu's you have
>> the more gain you will get from the improvements in I/O polling[1]. Also
>> the exact usage pattern matters.
>>
>>
>>> Is it reasonable to pick a point in master and use it on a production
>>> system after testing?
>>>
>>
>> I would take the latest tip of master and test that thoroughly for you
>> application. The things that we merge into master have gone through all our
>> testing before it is merged, so it is as stable as the maint branch.
>> However we make a lot more changes in master than in maint, so because of
>> that there will be a greater chance of some bug slipping through.
>>
>> If you do decide to give the improved I/O polling implementation a go,
>> please do come back with any negative or positive findings that you get!
>>
>> Lukas
>>
>> [1]: The largest change in the PR is not actually the ability to use
>> multiple pollsets, but that the polling has been lifted out to be done by
>> dedicated threads.
>>
>
>
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