Charlie Marsh 7da4af622f Optimize unbounded byte scans with memchr (#26265) ...

## Summary

This PR adds `memchr` for some low-hanging performance improvements
(namely, in MCP stdio, Ollama streaming, and full message-history
newline counts).

Codex produced the following release benchmarks:

| Operation | Before | After | Speedup |
| --- | ---: | ---: | ---: |
| MCP 1 MiB chunked line | 2.172 s | 3.984 ms | 545x |
| Ollama 1 MiB chunked line | 1.673 s | 2.790 ms | 600x |
| Count newlines in 10 MiB history | 132.83 ms | 20.05 ms | 6.6x |

With a "real" MCP setup (`ExecutorStdioServerLauncher` started a Python
MCP server, completed `initialize`, requested `tools/list`, and
deserialized a 1 MiB tool description over newline-delimited stdio),
it's about 16x faster end-to-end:

| Branch | 50 calls | Per call |
| --- | ---: | ---: |
| `main` | 862.53 ms | 17.25 ms |
| this branch | 53.89 ms | 1.08 ms |

`memchr` is already in our dependency tree and extremely widely used for
this kind of optimized scanning.

7da4af622f · 2026-06-04 09:53:08 -04:00

History

..

src

Optimize unbounded byte scans with memchr (#26265)

2026-06-04 09:53:08 -04:00

BUILD.bazel

Move message history out of core (#21278)

2026-05-06 08:35:42 -07:00

Cargo.toml

Optimize unbounded byte scans with memchr (#26265)

2026-06-04 09:53:08 -04:00