On 2/7/2024 10:12 AM, Andrea Righi wrote: > 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 Andrea, Thank you for providing these to us! - Joel
