[api] Optimize single vector writes to use write() instead of writev() - #10193
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To use the changes from this PR as an external component, add the following to your ESPHome configuration YAML file: external_components:
- source: github://pr#10193
components: [api]
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Codecov Report✅ All modified and coverable lines are covered by tests. Additional details and impacted files@@ Coverage Diff @@
## dev #10193 +/- ##
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Coverage 60.21% 60.21%
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Branches 1382 1382
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Pull Request Overview
This PR optimizes the API frame helper to use write() instead of writev() when sending single I/O vectors, reducing CPU overhead in the lwIP networking stack. The optimization specifically targets plaintext API connections which typically send single iovecs but were unnecessarily using the more complex writev() path.
- Adds conditional logic to detect single-vector writes and use
write()directly - Maintains backward compatibility by falling back to
writev()for multi-vector operations - Targets performance improvement for Bluetooth proxy and general API message sending
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What does this implement/fix?
This PR optimizes the API frame helper to use
write()instead ofwritev()when sending a single I/O vector, avoiding unnecessary overhead in the lwIP networking stack.When analyzing the ESPHome API send path for Bluetooth proxy performance, I found that plaintext API connections always use a single iovec, but still call
writev(). The lwIP implementation has no fast path for single vectors - it always goes through full vector processing vialwip_sendmsg(). This change detects single-vector writes and callswrite()directly, reducing CPU overhead for every API message.Types of changes
Related issue or feature (if applicable): N/A
Pull request in esphome-docs with documentation (if applicable): N/A
Test Environment
Example entry for
config.yaml:# No configuration changes required - this is an internal optimizationChecklist:
tests/folder).If user exposed functionality or configuration variables are added/changed: