`O_DIRECT` and other performance considerations about fs HOT 1 OPEN

It is worth noting that a web app will always be slower than a highly-optimized native app for highly storage-intensive workloads. The reason is that many such workloads just assume they have the entire machine to themselves. This allows all sorts of optimizations, such as busy-polling to eliminate interrupt overhead and using almost all of the machine’s memory for a massive userspace buffer pool. ScyllaDB even bypasses the kernel’s network stack, using DPDK (via SeaStar) to drive the network hardware directly! I would not at all be surprised if there is a bunch of hand-written assembler too.

For the web platform, I think the main advantage of efficient APIs is not to improve performance in benchmarks, but rather to improve responsiveness and use less power. What that means in practice is not something I am certain of at all, but I strongly believe that is the direction to go in.

from fs.