docs: update throttling #8854
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docs: update throttling #8854
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exterkamp
approved these changes
May 5, 2019
patrickhulce
approved these changes
May 5, 2019
docs/throttling.md
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| ## How do I get high-quality packet-level throttling? | ||
| 1. **Request-level** throttling, labeled in DevTools as _Applied throttling_, is how throttling is implemented with Chrome DevTools. In real mobile connectivity, latency affects things at the packet level rather than the request level. As a result, this throttling isn't highly accurate. It also has a few more downsides that are summarized in [Network Throttling & Chrome - status](https://docs.google.com/document/d/1TwWLaLAfnBfbk5_ZzpGXegPapCIfyzT4MWuZgspKUAQ/edit). The TLDR: while it's a [decent approximation](https://docs.google.com/document/d/10lfVdS1iDWCRKQXPfbxEn4Or99D64mvNlugP1AQuFlE/edit), it's not a sufficient model of a slow connection. The [multipliers used in Lighthouse](https://github.com/GoogleChrome/lighthouse/blob/3be483287a530fb560c843b7299ef9cfe91ce1cc/lighthouse-core/lib/emulation.js#L33-L39) attempt to correct for the differences. | ||
| 1. _Simulated throttling_, which Lighthouse uses by **default**, uses a simulation of a page load, based on the data observed in the initial unthrottled load. This approach which makes it both very fast and deterministic. However, due to the imperfect nature of predicting alternate execution paths, there is inherent inaccuracy that is summarized in this doc: [Lighthouse Metric Variability and Accuracy](https://docs.google.com/document/d/1BqtL-nG53rxWOI5RO0pItSRPowZVnYJ_gBEQCJ5EeUE/edit). The TLDR: while it's roughly as accurate or better than DevTools throttling for most sites, it suffers from edge cases and a deep investigation to performance should use _Packet-level_ throttling tools. |
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any reason "simulated throttling" is italics instead of bold+italic like the others?
(also seems like "request level" could be italics?)
| 1. The DevTools network throttling, which Lighthouse uses for `throttlingMethod='devtools'`, is implemented within Chrome at the _request-level_. As a result, it has some downsides that are now summarized in this doc: [Network Throttling & Chrome - status](https://docs.google.com/document/d/1TwWLaLAfnBfbk5_ZzpGXegPapCIfyzT4MWuZgspKUAQ/edit). The TLDR: while it's a [decent approximation](https://docs.google.com/document/d/10lfVdS1iDWCRKQXPfbxEn4Or99D64mvNlugP1AQuFlE/edit), it's not a sufficient model of a slow connection. The [multipliers used in Lighthouse](https://github.com/GoogleChrome/lighthouse/blob/3be483287a530fb560c843b7299ef9cfe91ce1cc/lighthouse-core/lib/emulation.js#L33-L39) attempt to correct for the differences. | ||
| 1. _Proxy-level_ throttling tools do not affect UDP data, so they're not recommended. | ||
| 1. _Packet-level_ throttling tools are able to make the most accurate network simulation. | ||
| Within web performance testing, there are four typical styles of throttling: |
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is the order going from least recommended to most recommended here? :)
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was sorting roughly on the context you needed to read the next one. but its kinda moot. just changed it to do simulated, devtools, proxy, packet.
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bunch of changes i wanted to make for a while