Richard Cochran wrote: > On Sun, Apr 10, 2011 at 01:22:08PM +0200, Gilles Chanteperdrix wrote: >> Also, about the performances, Xenomai 2.4 did not have the Xenomai >> preemptible context switches. Maybe with FCSE, it results in reduced >> latencies to disable this option in Xenomai 2.5. > > So, are you saying that XENO_HW_UNLOCKED_SWITCH=n might improve > latency? > > The help for this option says... > > This option reduces interrupt latency when costly cache and > TLB flushes are required to switch context, and may improve > concurrency on some SMP/multi-core systems as well. > > You definitely want to enable that option on embedded ARM > platforms. > > so I am confused.
Is is a trade-off. With this option enabled a context switch may be interrupted, this improves interrupt latency, but at the expense of scheduling latency. It makes a lot of sense without FCSE, when each context switch implies a 200us cache flush. A bit less with FCSE in guaranteed mode. -- Gilles. _______________________________________________ Xenomai-core mailing list Xenomaiemail@example.com https://mail.gna.org/listinfo/xenomai-core