AsyncEventSource queue management - #480
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willmmiles wants to merge 3 commits into
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willmmiles wants to merge 3 commits into
willmmiles wants to merge 3 commits into
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Track when we've filled the underlying socket and stop until we receive an ack. Reduces CPU usage blindly retrying when the buffer is full. Also fixes a correctness issue where a _runQueue which partially sends a message will still attempt to send the next message, which will tear if an ack arrives in between writes.
Drop redundant space check prior to attempting data send. add() has to check for available space internally, interlocked with the TCP layer; the additional check just wastes time.
As we are committed to ASYNC_WRITE_FLAG_COPY, we can release written event messages as soon as they are accepted by the TCP socket. Originally implemented in: - esphome#41 - mathieucarbou/ESPAsyncWebServer#92 Reverted by 43e0b5c in the hopes of supporting zero-copy TCP writes, but (as noted in that commit!) they are not supported on any Espressif platform, so the additional complexity buys no benefit.
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Thanks @willmmiles ! |
mathieucarbou
approved these changes
Sep 29, 2026
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I've done a fair amount of stress testing, this was one of the performance regression testing targets for the recent AsyncTCP work. I can't say I've tried every corner case though; if you know where the trouble spots are likely to be, please give those corners a poke! |
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Some fixes and performance improvements to
AsyncEventSourcethat fell out duringAsyncTCPregression testing._runQueuein this sequence:_runQueuefills the output buffer with a partial frameasyncthread - the space is made available as soon as it touches LwIP`_runQueuestill considers the next message, sending a part of the next messagewrite()reduces round trips with the LwIP core.