> >> > >> I have done some basic research about hrtimer_interrupt() latency on my > >> HW with latest Linux kernel. I have compared below cases: > >> > >> case a: 1000HZ + lazy + nocb_all_cpus > >> case b: 1000HZ + nocb_all_cpus > >> > >> I used "ftrace" to measure time(in microseconds). Steps: > >> > >> echo 0 > tracing_on > >> echo function_graph > current_tracer > >> echo funcgraph-proc > trace_options > >> echo funcgraph-abstime > trace_options > >> echo hrtimer_interrupt > set_ftrace_filter > >> > >> fio --rw=write --bs=1M --size=1G --numjobs=8 --name=worker --time_based > >> --runtime=50& > >> > >> echo 1 > tracing_on; sleep 10; echo 0 > tracing_on > >> > >> data is based on 10 seconds collection: > >> > >> <case a> > >> 6 2102 ############################################################ > >> 8 2079 ############################################################ > >> 10 1464 ########################################## > >> 7 897 ########################## > > So first column is microseconds and second one is count? > Right!
> >> 9 625 ################## > >> 12 490 ############## > >> 13 479 ############## > >> 11 289 ######### > >> 5 249 ######## > >> 14 124 #### > >> 15 72 ### > >> 16 41 ## > >> 17 24 # > >> 4 22 # > >> 18 12 # > >> 22 2 # > >> 19 1 # > >> <case a> > >> > >> <case b> > >> 9 1658 ############################################################ > >> 13 1308 ################################################ > >> 12 1224 ############################################# > > Assuming that, it does seem the "best" case is off by 3 microseconds (9 vs 6), > still would not warrant being regarded a bug and possibly just in the noise. > I also think it is a noise.
