"Niklas Cassel" <cassel@xxxxxxxxxx> writes: > 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 ? Yes. > > It would be interesting to test an older kernel version, and see if it > is e.g. a scheduler bug. Yes, I did not do that. I should collect some more detailed data for past kernels. > 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. > I'll try that, thanks. Best regards, Andreas Hindborg
