On 04/04/2018 16:19, Stefan Esser wrote: > I have identified the cause of the extremely low I/O performance (2 to 6 read > operations scheduled per second). > > The default value of kern.sched.preempt_thresh=0 does not give any CPU to the > I/O bound process unless a (long) time slice expires (kern.sched.quantum=94488 > on my system with HZ=1000) or one of the CPU bound processes voluntarily gives > up the CPU (or exits). > > Any non-zero value of preemt_thresh lets the system perform I/O in parallel > with the CPU bound processes, again.
Let me guess... you have a custom kernel configuration and, unlike GENERIC (assuming x86), it does not have 'options PREEMPTION'? -- Andriy Gapon _______________________________________________ freebsd-current@freebsd.org mailing list https://lists.freebsd.org/mailman/listinfo/freebsd-current To unsubscribe, send any mail to "freebsd-current-unsubscr...@freebsd.org"
