Dual RTX 3090 (TP=2) vs single: a controlled A/B on your harness — +16-35%, DFlash2 residency, and the KV_MEM pin

Hi, and first of all — thank you for this repo. The care in it is unusual: the gotchas file alone saved us a day, and having every claim tied to a harness you ship means an outside report like this one can actually be compared to yours instead of talking past it. We really appreciate the work. We have a dual-3090 box and wanted to share the tests we were able to run on it. The README notes that multi-GPU "goes through untouched … every multi-GPU number in the issues is a user report rather than something I have reproduced", and #7 invites numbers, so we hope this is useful rather than noise. We ran it as a **controlled A/B** — same box, same install, same `bench/run_benchmarks.sh single`, same session, with `--tensor-parallel-size 2` as the only variable — because what seemed missing wasn't a dual-GPU number but the **delta**: how much the second card is actually worth on this stack, measured against itself. Two of the findings touch things you documented deliberately (the DFlash2 single-stream guidance and the pinned `KV_MEM`), so we've tried to show our work and flag exactly what we did and didn't measure. If we've misread either, we'd rather be corrected than have the numbers stand. Happy to re-run anything, share raw logs, or test a patch on this hardware. --- ## TL;DR 1. **The second 3090 pays off across the whole concurrency range**, not just in capacity: **+16% to +32%** with MTP, **+19% to +35%** with DFlash2 (greedy, decode tok/s). Best result: **161.6 tok...