Hello Andreas, On Tue, Jan 21, 2025 at 01:51:11PM +0100, Andreas Hindborg wrote: > Hi Jan, > > "Jan Kara" <jack@xxxxxxx> writes: > > > Hi! > > > > On Tue 21-01-25 12:13:48, Andreas Hindborg via Lsf-pc wrote: > >> I would like to propose that we have a session on Rust in the block > >> layer again this year. Specifically I would like to discuss some rather > >> puzzling results I observe when I benchmark the C and Rust null block > >> drivers. I did a write up of the challenges I face at [1]. The > >> observations are not tied to rust, they also manifest in the C driver. > > > > The results are indeed somewhat curious. One factor I didn't see addressed > > in your blog is CPU scheduling. I've seen in the past cases where IO tasks > > were getting migrated across cores leading to jumps in perfomance. Did you > > try binding fio jobs to one CPU each? > > Yes, I am pinning the io jobs to cores with fio options `cpus_allowed=0-<jobs>` > and `--cpus_allowed_policy=split` so I get 1 job per core. > > The kernel is configured with PREEMPT_NONE=y. "I also cover a problem with the benchmark results that manifested during testing for v6.12-rc2." I assume that all the results on: https://metaspace.github.io/2024/12/02/problems-in-benchmark-land.html are with kernel v6.12-rc2 ? It would be interesting to test an older kernel version, and see if it is e.g. a scheduler bug. You might also want to test with this series applied (which landed last minute before v6.13 was tagged): https://lore.kernel.org/lkml/20250119110410.GAZ4zcKkx5sCjD5XvH@fat_crate.local/T/#u It fixes bugs that were introduced in v6.12-rc1 and v6.7-rc2 respectively. Kind regards, Niklas
