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[wasm] spread WS based timers over next 6 minutes to prevent heavy throttling #57745

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pavelsavara merged 8 commits into from
Aug 26, 2021
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[wasm] spread WS based timers over next 6 minutes to prevent heavy throttling #57745

pavelsavara merged 8 commits into from
Aug 26, 2021

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@pavelsavara pavelsavara commented Aug 19, 2021 •
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Problem

Chromium browsers throttle setTimeout frequency on inactive pages to 1 sec almost immediately.
5 minutes later they throttle heavily to wakeup each 60 seconds.
That breaks dotnet Timer expectations and also threadpool.

The heavy throttling could be lifted back to 1sec if there was WebSocket activity.
https://developer.chrome.com/blog/timer-throttling-in-chrome-88/#intensive-throttling

Implementation

The idea is to cover the future 6 minutes with "wakeup" timer, each 1 second apart from each other.
1 second, because is the light throttling rate, so it would not help to try to do it more often.
It should be triggered from WS event, so that it's only 1 deep from it.
Every subsequent call would schedule only for uncovered future.

There is [OuterLoop] unit test for this.

Fixes #51041

@pavelsavara pavelsavara added the arch-wasm WebAssembly architecture label Aug 19, 2021
@pavelsavara pavelsavara requested review from kg and lewing August 19, 2021 17:27
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Issue Details

Fixes #51041

Author: pavelsavara
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arch-wasm
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pavelsavara commented Aug 19, 2021 •
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Right now, I'm not clear if 6 minutes is right time span.
Also I plan to implement OuterLoop unit test for it yet.

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pavelsavara commented Aug 20, 2021

This is necessary infrastructure change for the automated test. It's still quite fragile.
dotnet/xharness#695

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pavelsavara commented Aug 23, 2021

/azp run runtime-libraries-mono outerloop

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@pavelsavara pavelsavara force-pushed the wasm_prevent_timer_throttling branch from bec2dfc to 043e566 Compare August 23, 2021 13:37
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pavelsavara commented Aug 23, 2021 •
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New xharness binaries are in.

@pavelsavara pavelsavara marked this pull request as ready for review August 23, 2021 15:49
@pavelsavara pavelsavara force-pushed the wasm_prevent_timer_throttling branch from aa34508 to 42fc2ea Compare August 25, 2021 11:18
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pavelsavara commented Aug 25, 2021

/azp run runtime-libraries-mono outerloop

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pavelsavara commented Aug 25, 2021

/azp run runtime-libraries-mono outerloop

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pavelsavara commented Aug 25, 2021

/azp run runtime-libraries-mono outerloop

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pavelsavara commented Aug 25, 2021

/azp run runtime-libraries-mono outerloop

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pavelsavara commented Aug 25, 2021

Outerloop issue is Unable to open X display. for the new System.Net.WebSockets.Client.Wasm.Tests, which makes sense.
But throttling is not testable without real visible browser UI.

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kg commented Aug 25, 2021

IIRC there are ways to run chromium headless with a 'fake' framebuffer, window etc. Not sure which one we'd use here, or whether it would actually trigger this. Another option would be a headless X instance paired to VNC, I know people do that for tests sometimes.

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pavelsavara commented Aug 25, 2021

I just excluded the test from CI, making it manual test.

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Everything looks fine to me

@pavelsavara pavelsavara merged commit 5eaa911 into dotnet:main Aug 26, 2021
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pavelsavara commented Aug 26, 2021

/backport to release/6.0-rc1

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github-actions bot commented Aug 26, 2021

Started backporting to release/6.0-rc1: https://github.com/dotnet/runtime/actions/runs/1169555771

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@karelz karelz added this to the 7.0.0 milestone Aug 26, 2021
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@pavelsavara pavelsavara deleted the wasm_prevent_timer_throttling branch January 4, 2022 13:03
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@kg kg kg approved these changes

@lewing lewing Awaiting requested review from lewing lewing is a code owner

@marek-safar marek-safar Awaiting requested review from marek-safar

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arch-wasm WebAssembly architecture area-System.Runtime.InteropServices.JavaScript

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[WASM] Chrome timer throttling affects runtime

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@pavelsavara @kg @karelz