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Re: Context switch latency in tickless isolated CPU

From "Paul E. McKenney" <paulmck@linux.vnet.ibm.com>
Newsgroups linux.kernel
Subject Re: Context switch latency in tickless isolated CPU
Date 2016-08-21 17:00 +0200
Message-ID <s8Co9-1CP-7@gated-at.bofh.it> (permalink)
References <s72G6-5IV-7@gated-at.bofh.it> <s7mbL-2j1-7@gated-at.bofh.it> <s7mbL-2j1-5@gated-at.bofh.it> <s7RfA-5Cv-7@gated-at.bofh.it> <s8z6W-88W-21@gated-at.bofh.it>
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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@infradead.org> 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

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Thread

Context switch latency in tickless isolated CPU GeHao Kang <kanghao0928@gmail.com> - 2016-08-17 08:40 +0200
  Re: Context switch latency in tickless isolated CPU GeHao Kang <kanghao0928@gmail.com> - 2016-08-18 05:30 +0200
    Re: Context switch latency in tickless isolated CPU Peter Zijlstra <peterz@infradead.org> - 2016-08-19 14:40 +0200
      Re: Context switch latency in tickless isolated CPU GeHao Kang <kanghao0928@gmail.com> - 2016-08-21 13:30 +0200
        Re: Context switch latency in tickless isolated CPU "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-08-21 17:00 +0200
          Re: Context switch latency in tickless isolated CPU GeHao Kang <kanghao0928@gmail.com> - 2016-08-22 11:50 +0200
            Re: Context switch latency in tickless isolated CPU "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-08-22 16:50 +0200
              Re: Context switch latency in tickless isolated CPU Mark Hounschell <markh@compro.net> - 2016-08-22 17:20 +0200
                Re: Context switch latency in tickless isolated CPU "Paul E. McKenney" <paulmck@linux.vnet.ibm.com> - 2016-08-22 17:40 +0200
                Re: Context switch latency in tickless isolated CPU Mark Hounschell <markh@compro.net> - 2016-08-22 18:50 +0200

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