Just to close this off, PR was declined: https://github.com/elixir-lang/elixir/pull/12229. Advice is to reach into `:os.perf_counter` for the use case.
On Friday, November 4, 2022 at 10:25:38 p.m. UTC-4 halos...@gmail.com wrote: > On Fri, Nov 4, 2022 at 9:29 PM Mat Trudel <m...@geeky.net> wrote: > >> Hey Austin! >> >> I realize that making all of the relevant calls to Erlang directly is >> possible (I might even say straightforward), but the problem is that >> it's not *discoverable*. The intent here is to 'pave the golden path' and >> help make the existence and usage of perf_counter clear & >> straightforward for folks, and to do so in the first place they're likely >> to look (namely alongside the other `*_time` functions in `System`). >> >> I'm a pretty experienced and extremely curious guy who's been doing this >> for quite a while, and if `perf_counter` is news to me, it's likely news >> to a lot of other people as well. The intent of this proposal isn't to make >> things *possible*, it's to make them *discoverable*. >> > > Fair enough and a good reason. When I was looking at implementing > Telemetry (because this was a good opportunity to dig deep to determine how > to adopt it for our main application), I looked at how many common packages > were using it and no one was calling `System.monotonic_type` or > `System.system_time`, despite the inlining. > > You’re right that `:os.perf_counter` is news to me, too, but I’m not sure > how or whether *for my use case* it would be better to use that or > monotonic time, especially as everyone else is using monotonic time. For > the very low level stuff that you’re doing with Thousand Island…the > difference might be worth it. > > >> Also, neat context-driven start_span / stop_span model! I've been >> thinking about something similar for my upcoming telemetry work in Bandit >> and it's encouraging to see prior art for the idea! >> > > I’m not going to claim credit for the model—they are basically the models > that `Plug.Telemetry` and `:telemetry.span` use, and similar (in many ways) > to what `Télemetria` and `Sybil` do, just honed razor fine for the cases > that I felt were worth supporting. I’m also deeply grateful to the Absinthe > tests for seeing how tests should be written for using Telemetry. > > I think that for the next *major* version (a while from now), I’m going to > be shifting it into two or more *different* packages so that there’s a core > Erlang version (so that the functionality is available for all Beam users) > and then there are utility packages for Elixir packages. In the interim, > I’m adding the Telemetry support and will later be adding a `Req` plug-in. > > -a > > On Friday, November 4, 2022 at 7:05:50 p.m. UTC-4 halos...@gmail.com >> wrote: >> >>> I just implemented some telemetry in a library that should be usable in >>> hot paths (but likely has more expensive costs than the telemetry path) and >>> I didn’t use any of the Elixir wrappers to the Erlang module functions, but >>> called them directly. >>> >>> https://github.com/KineticCafe/app_identity/pull/3 >>> >>> Do we need this? >>> >>> -a >>> >>> On Fri, Nov 4, 2022 at 4:49 PM Mat Trudel <m...@geeky.net> wrote: >>> >>>> Using tools such as telemetry in a performant manner requires access to >>>> some sort of low cost timing primitive to be able to calculate intervals. >>>> The community seems to use a mixture of `System.system_time/0` and/or >>>> `System.monotinic_time/0` to accomplish this, though neither of these are >>>> built specifically for purpose, and neither are terribly performant on >>>> super hot paths [1]. >>>> >>>> As it turns out, Erlang provides a tool for exactly this purpose, >>>> though Elixir doesn't expose it natively. That tool is >>>> `:os.perf_counter/1`: >>>> https://www.erlang.org/doc/man/os.html#perf_counter-1 >>>> >>>> It would be good to have first-class access to this in Elixir. >>>> Therefore, it is proposed to add the following to System: >>>> >>>> * Add `System.perf_counter/0` & `System.perf_counter/1` as thin >>>> wrappers around `:os.perf_counter`, in the same manner as is currently >>>> done >>>> for `System.system_time` et al >>>> >>>> * Add support for `perf_counter` to `System.convert_time_unit/3`. This >>>> is already supported in the underlying `:erlang.convert_time_unit/3`, it's >>>> just a matter of adding a clause to the private `normalize_time_unit` >>>> function. >>>> >>>> Combined, these will allow for *significantly* faster interval >>>> calculation, which should help speed up all sorts of hot telemetry paths. >>>> >>>> In practice, `perf_counter` is about twice as fast as `system_time`. A >>>> quick comparison (run on an M1 MacBook Air running 1.14/OTP 25.1): >>>> >>>> ``` >>>> Mix.install([{:benchee, "~> 1.0", only: :dev}]) >>>> >>>> Benchee.run(%{ >>>> system_time: &System.system_time/0, >>>> monotonic_time: &System.monotonic_time/0, >>>> perf_counter: &:os.perf_counter/0 >>>> }) >>>> >>>> Name ips average deviation median >>>> 99th % >>>> perf_counter 54.03 M 18.51 ns ±439.35% 18.33 ns >>>> 20.01 ns >>>> monotonic_time 28.10 M 35.58 ns ±2758.64% 33.30 ns >>>> 41.70 ns >>>> system_time 23.44 M 42.67 ns ±8964.02% 37.50 ns >>>> 45.90 ns >>>> >>>> Comparison: >>>> perf_counter 54.03 M >>>> monotonic_time 28.10 M - 1.92x slower +17.08 ns >>>> system_time 23.44 M - 2.31x slower +24.16 ns >>>> ``` >>>> >>>> If folks are onboard I can get this implemented immediately. >>>> >>>> m. >>>> >>>> [1] https://github.com/mtrudel/thousand_island/issues/1, among others >>>> >>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "elixir-lang-core" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to elixir-lang-co...@googlegroups.com. >>>> To view this discussion on the web visit >>>> https://groups.google.com/d/msgid/elixir-lang-core/9d4111e5-4799-4781-bbf1-43dae14dcb94n%40googlegroups.com >>>> >>>> <https://groups.google.com/d/msgid/elixir-lang-core/9d4111e5-4799-4781-bbf1-43dae14dcb94n%40googlegroups.com?utm_medium=email&utm_source=footer> >>>> . >>>> >>> >>> >>> -- >>> Austin Ziegler • halos...@gmail.com • aus...@halostatue.ca >>> http://www.halostatue.ca/ • http://twitter.com/halostatue >>> >> -- >> You received this message because you are subscribed to the Google Groups >> "elixir-lang-core" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to elixir-lang-co...@googlegroups.com. >> > To view this discussion on the web visit >> https://groups.google.com/d/msgid/elixir-lang-core/e9f7df4a-5ee1-4ca3-8111-c9d221ebff75n%40googlegroups.com >> >> <https://groups.google.com/d/msgid/elixir-lang-core/e9f7df4a-5ee1-4ca3-8111-c9d221ebff75n%40googlegroups.com?utm_medium=email&utm_source=footer> >> . >> > > > -- > Austin Ziegler • halos...@gmail.com • aus...@halostatue.ca > http://www.halostatue.ca/ • http://twitter.com/halostatue > -- You received this message because you are subscribed to the Google Groups "elixir-lang-core" group. 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