On 1/17/24 12:06, Jens Axboe wrote:
Case in point, I spent 10 min hacking up some smarts on the insertion and dispatch side, and then we get: IOPS=2.54M, BW=1240MiB/s, IOS/call=32/32 or about a 63% improvement when running the _exact same thing_. Looking at profiles: - 13.71% io_uring [kernel.kallsyms] [k] queued_spin_lock_slowpath reducing the > 70% of locking contention down to ~14%. No change in data structures, just an ugly hack that: - Serializes dispatch, no point having someone hammer on dd->lock for dispatch when already running - Serialize insertions, punt to one of N buckets if insertion is already busy. Current insertion will notice someone else did that, and will prune the buckets and re-run insertion. And while I seriously doubt that my quick hack is 100% fool proof, it works as a proof of concept. If we can get that kind of reduction with minimal effort, well...
If nobody else beats me to it then I will look into using separate locks in the mq-deadline scheduler for insertion and dispatch. Bart.
