gh-146507: Make _SelectorTransport.get_write_buffer_size() O(1)#146518
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kumaraditya303 merged 5 commits intopython:mainfrom Mar 27, 2026
Merged
gh-146507: Make _SelectorTransport.get_write_buffer_size() O(1)#146518kumaraditya303 merged 5 commits intopython:mainfrom
kumaraditya303 merged 5 commits intopython:mainfrom
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Maintain a running _buffer_size counter instead of recalculating with sum(map(len, _buffer)) on every call. This matches the O(1) pattern already used by _SelectorDatagramTransport and _ProactorBaseWritePipeTransport in the same codebase.
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kumaraditya303
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Mar 27, 2026
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Closes #146507
_SelectorTransport.get_write_buffer_size()recalculates the total buffer size by iterating the entire_bufferdeque on every call. Since this is called from_maybe_pause_protocol()after everywrite(), it creates O(n²) behavior when chunks accumulate faster than they drain.This replaces the O(n) sum with a running
_buffer_sizecounter, matching the pattern already used by_SelectorDatagramTransportand_ProactorBaseWritePipeTransport.Also fixes a pre-existing issue in
_write_sendwhereBlockingIOErrorafterpopleft()would silently drop the buffer entry — the data is now put back.