For us, it was IO actually: doing IO concurrently (Lwt) and letting the one core schedule the IO worked quite well for a long time, but then we started targetti

For us, it was IO actually: doing IO concurrently (Lwt) and letting the one core schedule the IO worked quite well for a long time, but then we started targetting NVMe devices... Now just the scheduling of the IO would fill up the core without coming even close saturating the device. We ended up splitting the device and using multiple processes but that was suboptimal.