File system and network stacks in Userland: why we must use them in 2022

IO-performance becomes increasingly important:

• we have more and more cores,
• PCIe Gen3 is finally turning into PCIe Gen5 and for now it stops being the bottleneck,
• NVMe drives and 200G NICs means the network is faster and fast.

Stacks that were OK-ish in the past are not OK now. You can't saturate the HW IO capacity while doing context switches, wakeups in the kernel etc. So what before was an "option" is actually a MUST HAVE for most of the high performance applications.