Optimize critical I/O path for input latency#4145
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This reduces demo input latency on my mac approx 10ms -> 4ms
This seems to make little difference but it's more correct as we want to write as fast as possible to minimize input latency
- Optimize critical I/O path for input latency xtermjs/xterm.js#4145 - Add PriorityTaskQueue xtermjs/xterm.js#4144 - Use the browser's IdleDeadline to determine max task time xtermjs/xterm.js#4143 - Defer paused renderer resize to idle callback xtermjs/xterm.js#4142 - Do char atlas warmup via new IdleTaskQueue xtermjs/xterm.js#4141 - Share rgba vars throughout Color.ts, fast setTheme parseColor xtermjs/xterm.js#4140 - Optimize contexts for reading frequently xtermjs/xterm.js#4137 - Fix width of upper 1/8 block char xtermjs/xterm.js#4134 Fixes #161323
| if (!this._writeBuffer.length) { | ||
| this._bufferOffset = 0; | ||
| setTimeout(() => this._innerWrite()); | ||
| queueMicrotask(() => this._innerWrite()); |
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This should be safe with queueMicrotask - reason: this code path is only entered, if the write queue was empty before, which guarantees, that there happened a screen refresh before.
| this._bufferOffset = 0; | ||
| } | ||
| setTimeout(() => this._innerWrite()); | ||
| queueMicrotask(() => this._innerWrite()); |
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Not so sure about queueMicrotask here - imho this will skip any screen refreshs in between, if the write queue never drops empty? (This edge case might be provokable by tiny messages at sync promisified term.write calls while the write queue never drops empty...)
There are more edge cases linked to direct microtask usage - imho chrome and firefox prioritize them differently (dont remember the details atm).
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Opps. You're right, will fix
There are more edge cases linked to direct microtask usage - imho chrome and firefox prioritize them differently (dont remember the details atm).
I didn't test in Firefox but this should only matter if queueMicrotask ends up slower than setTimeout which I think would be against the spec?
- Optimize critical I/O path for input latency xtermjs/xterm.js#4145 - Add PriorityTaskQueue xtermjs/xterm.js#4144 - Use the browser's IdleDeadline to determine max task time xtermjs/xterm.js#4143 - Defer paused renderer resize to idle callback xtermjs/xterm.js#4142 - Do char atlas warmup via new IdleTaskQueue xtermjs/xterm.js#4141 - Share rgba vars throughout Color.ts, fast setTheme parseColor xtermjs/xterm.js#4140 - Optimize contexts for reading frequently xtermjs/xterm.js#4137 - Fix width of upper 1/8 block char xtermjs/xterm.js#4134 Fixes microsoft#161323
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This reduced input latency from about 10ms -> 4ms on my mac (measurement based on devtools tasks).
Before server microtask:
After server microtask:
After server microtask and write buffer microtask: