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Make your QEMU faster (2022)
The work on QEMU and this post was paid for by Determinate Systems, and the post was co-published on the Determinate Systems blog. Background NixOS uses virtual machines based on QEMU extensively for running its test suite.
Moreover, some inspection of QSIMPLEQ (QEMU simple queue) reveals that it’s implemented as a linked list, a data structure which tends to exhibit poor cache locality. The exact real-world performance characteristics are significantly more complex than with the linked list, and there may be marginally more suitable data structures (or hash table implementations) out there, but we’re looking for a big easy win and not micro-optimisation here. Forgetting to reply-all when answering review comments, so that the reply is visible to everyone interested and not just the reviewer Missing the version tag on a resubmission (in my case, this was because of misleading docs) Sending a resubmission as a reply to the previous thread (that was just me failing to read the docs) Losing a bunch of patch-documenting work while using git-publish because git send-email failed (nixpkgs does not enable Git’s email functionality in the default package, and git-publish unconditionally deletes the working files once the send command has run).
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