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I have a great deal of experience in running very large memory-mapped databases using LMDB.

The default Linux settings dealing with memory mapped files are pretty horrible. The observed poor performance is directly related to not configuring several very important kernel parameters.

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Can you share a couple examples of those parameters?

This describes the relevant kernel variables:

https://synapse.docs.vertex.link/en/latest/synapse/devguides...

These settings control writing back modified pages. The experiments in the paper are read-only. With writes the situation is even worse than shown in the paper (though tuning these settings may help a bit).

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