[Xenomai] Low-latency desktop setting

Gilles Chanteperdrix gilles.chanteperdrix at xenomai.org
Thu Aug 28 22:02:15 CEST 2014


On 08/28/2014 09:49 PM, Yogi A. Patel wrote:
> In configuring the kernel (after patching with xenomai), there is an
> option to change the preemption model to "low-latency desktop".
> 
> Is this a setting that should be set? Or should it be left to the
> default preemption mode??
> 
> How does this setting affect the real-time performance of a xenomai
> enabled kernel?

This option is about Linux preemption, it affects how often Linux is
willing to preempt itself, in the throughput/latency fight, it gives
advantage to (Linux) latency at the expense of througput. It does not
affect Xenomai directly, but rather indirectly: it creates a code with a
lower "density", by littering the Linux kernel execution with checks for
the need of rescheduling, so that Linux has a larger pollution effect on
caches. In my experience, you get slightly lower Linux latencies by
turning CONFIG_PREEMPT off (selecting CONFIG_PREEMPT_NONE).

-- 
                                                                Gilles.




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