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MegaRedHand merged 1 commit into from
Apr 16, 2026
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Document sysctl tuning for QUIC UDP buffer sizes #296

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7 changes: 7 additions & 0 deletions README.md
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Expand Up @@ -40,6 +40,13 @@ make run-devnet
This generates fresh genesis files and starts all configured clients with metrics enabled.
Press `Ctrl+C` to stop all nodes.

> **Note:** On Linux, QUIC performance benefits from larger UDP receive buffers. If you see warnings about buffer sizes, increase the kernel limit:
> ```sh
> sudo sysctl -w net.core.rmem_max=7340032
> sudo sysctl -w net.core.wmem_max=7340032
> ```
> To persist across reboots, add to `/etc/sysctl.conf`. For Docker, pass `--sysctl net.core.rmem_max=7340032 --sysctl net.core.wmem_max=7340032`.
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P2 /etc/sysctl.conf note omits apply-without-reboot step

The note says "add to /etc/sysctl.conf" but doesn't show what to write or how to activate it without rebooting. Users will likely need to run sudo sysctl -p to apply immediately. A self-contained example would be clearer:

Suggested change
> To persist across reboots, add to `/etc/sysctl.conf`. For Docker, pass `--sysctl net.core.rmem_max=7340032 --sysctl net.core.wmem_max=7340032`.
> To persist across reboots, add the following lines to `/etc/sysctl.conf` and run `sudo sysctl -p` to apply without rebooting. For Docker, pass `--sysctl net.core.rmem_max=7340032 --sysctl net.core.wmem_max=7340032`.
Prompt To Fix With AI 
This is a comment left during a code review.
Path: README.md
Line: 48

Comment:
**`/etc/sysctl.conf` note omits apply-without-reboot step**

The note says "add to `/etc/sysctl.conf`" but doesn't show what to write or how to activate it without rebooting. Users will likely need to run `sudo sysctl -p` to apply immediately. A self-contained example would be clearer:

```suggestion
> To persist across reboots, add the following lines to `/etc/sysctl.conf` and run `sudo sysctl -p` to apply without rebooting. For Docker, pass `--sysctl net.core.rmem_max=7340032 --sysctl net.core.wmem_max=7340032`.
```

How can I resolve this? If you propose a fix, please make it concise.

Comment on lines +43 to +48
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P2 Docker --sysctl flag not applicable to Compose-based devnet

make run-devnet uses lean-quickstart, which is Docker Compose based. The --sysctl flag shown applies to docker run; for Compose deployments the equivalent is a sysctls: key in the service definition. Users trying to apply this hint to the devnet may be confused. Consider clarifying that the Docker note applies to standalone docker run invocations, or point to modifying the Compose file for the devnet case.

Prompt To Fix With AI 
This is a comment left during a code review.
Path: README.md
Line: 43-48

Comment:
**Docker `--sysctl` flag not applicable to Compose-based devnet**

`make run-devnet` uses `lean-quickstart`, which is Docker Compose based. The `--sysctl` flag shown applies to `docker run`; for Compose deployments the equivalent is a `sysctls:` key in the service definition. Users trying to apply this hint to the devnet may be confused. Consider clarifying that the Docker note applies to standalone `docker run` invocations, or point to modifying the Compose file for the devnet case.

How can I resolve this? If you propose a fix, please make it concise.


> **Important:** When running nodes manually (outside `make run-devnet`), at least one node must be started with `--is-aggregator` for attestations to be aggregated and included in blocks. Without this flag, the network will produce blocks but never finalize.

For custom devnet configurations, go to `lean-quickstart/local-devnet/genesis/validator-config.yaml` and edit the file before running the command above. See `lean-quickstart`'s documentation for more details on how to configure the devnet.
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