2021345 - Move WebSerial reads to a separate thread for performance/power reasons

Status: RESOLVED FIXED

(Core :: DOM: Web Serial, enhancement)

Description

[Greg Stoll :gstoll]

Right now in dom/webserial/SerialPlatformRunnable.cpp we poll the serial port device and redispatch fairly frequently (at time of writing kReadPollIntervalMs is 20) to avoid missing data. If we moved this to a separate thread for each device, we could instead just block the thread, similar to what Chromium does.

Comment 1

[Greg Stoll :gstoll]

Attachment: Bug 2021345 - make WebSerial reads asynchronous r=nika!

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/f1ea8daf3b5b
https://hg.mozilla.org/integration/autoland/rev/e526f0c103e9
make WebSerial reads asynchronous r=nika,jld

Comment 3

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/e526f0c103e9

Comment 4

[Phabricator Automation]

firefox-beta Uplift Approval Request

• User impact if declined/Reason for urgency: poor performance for reading from WebSerial devices
• Code covered by automated testing?: yes
• Fix verified in Nightly?: no
• Needs manual QE testing?: no
• Steps to reproduce for manual QE testing: n/a
• Risk associated with taking this patch: low
• Explanation of risk level: Reworks how we read from WebSerial devices, but should only affects those devices and we've done manual validation for the most common ones.
• String changes made/needed?: n/a
• Is Android affected?: no

Comment 5

[Greg Stoll :gstoll]

Attachment: Bug 2021345 - make WebSerial reads asynchronous

Note that this relies on the new PlatformPipeReader class added for
bug 2031881. Using this and NS_AsyncCopy() means that we no longer have
to poll for new data from serial devices, which means we're faster to
receive that data and also yields better power usage.

Original Revision: https://phabricator.services.mozilla.com/D294690

Comment 6

[Pulsebot]

https://github.com/mozilla-firefox/firefox/commit/79812a2681ba
https://hg.mozilla.org/releases/mozilla-beta/rev/3ff6f51ed3df