Re: Context switch latency in tickless isolated CPU

[Paul E. McKenney]

On Sun, Aug 21, 2016 at 07:26:04PM +0800, GeHao Kang wrote:
> On Fri, Aug 19, 2016 at 8:34 PM, Peter Zijlstra <peterz@xxxxxxxxxxxxx> wrote:
> 
> > Why are you wanting to use nohz_full if you do syscalls?
> 
> We hope to reduce the overhead of the tick while the real time
> applications run,
> and these applications might do some syscalls to operate the I/O devices like
> EtherCAT.

If latency is all you care about, one approach is to map the device
registers into userspace and do the I/O without assistance from the
kernel.

Alternatively, use in-memory mailbox/queuing techniques to hand the
I/O off to some other thread.

							Thanx, Paul