On Wed, Feb 07, 2024 at 02:04:12PM +0100, Uladzislau Rezki wrote: > > > > > > I repeated some tests in a more isolated environment and posted the > > > results here: > > > https://discourse.ubuntu.com/t/enable-low-latency-features-in-the-generic-ubuntu-kernel-for-24-04/42255 > > > > > > Highlights: > > > > > > - stress-ng --matrix seems quite unpredictable to be used a benchmarks > > > in this scenario (the bogo-ops/s are very susceptible to any kind of > > > interference, so even if in the long runs NO_HZ_FULL still seems to > > > provide some benefits looking at the average, we also need to > > > consider that there might be a significant error in the measurements, > > > standard deviation was pretty high) > > > > > > - fio doing short writes (in page cache) seems to perform like 2x > > > better in terms of iops with nohz_full, respect to the other cases > > > and it performs 2x slower with large IO writes (not sure why... need > > > to investigate more) > > > > > > - with lazy RCU enabled hrtimer_interrupt() takes like 2x more to > > > return, respect to the other cases (is this expected?) > > > > This last is surprising at first glance, but I could be missing > > something. Joel, Uladzislau, thoughts? > > > Could you please share the steps how you run "fio" tests? For short writes I was running something like this (on a 8 cores system): $ fio --rw=write --bs=1M --size=32M --numjobs=8 --name=worker --time_based --runtime=300 Larger writes: $ fio --rw=write --bs=1M --size=1G --numjobs=8 --name=worker --time_based --runtime=300 Thanks, -Andrea
