* [Xenomai-core] Latency spots due to involuntary mode switches to secondary mode.
@ 2010-01-08 10:14 Gilles Chanteperdrix
2010-01-17 21:56 ` Philippe Gerum
0 siblings, 1 reply; 2+ messages in thread
From: Gilles Chanteperdrix @ 2010-01-08 10:14 UTC (permalink / raw)
To: Xenomai core
Hi,
due to bugs, it may happen that the latency test spots are due to
involuntary mode switches to secondary mode. This is bad, because users
testing xenomai quickly on their platform may find a bad latency, and go
quickly to conclusions without even posting a mail on the mailing lists.
Avoiding this looks simple: we should enable T_WARNSW on the sampling
thread, and make it the default behaviour. But unfortunately, there are
platforms around such as some low-end ppc where switches to secondary
mode are normal, so stopping the test when hitting such mode switches
may not be the best thing to do.
So, what do you think should be done?
--
Gilles.
^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [Xenomai-core] Latency spots due to involuntary mode switches to secondary mode.
2010-01-08 10:14 [Xenomai-core] Latency spots due to involuntary mode switches to secondary mode Gilles Chanteperdrix
@ 2010-01-17 21:56 ` Philippe Gerum
0 siblings, 0 replies; 2+ messages in thread
From: Philippe Gerum @ 2010-01-17 21:56 UTC (permalink / raw)
To: Gilles Chanteperdrix; +Cc: Xenomai core
On Fri, 2010-01-08 at 11:14 +0100, Gilles Chanteperdrix wrote:
> Hi,
>
> due to bugs, it may happen that the latency test spots are due to
> involuntary mode switches to secondary mode. This is bad, because users
> testing xenomai quickly on their platform may find a bad latency, and go
> quickly to conclusions without even posting a mail on the mailing lists.
>
> Avoiding this looks simple: we should enable T_WARNSW on the sampling
> thread, and make it the default behaviour. But unfortunately, there are
> platforms around such as some low-end ppc where switches to secondary
> mode are normal, so stopping the test when hitting such mode switches
> may not be the best thing to do.
>
> So, what do you think should be done?
>
Let's report those switches in the test output without stopping it, so
that we may have some hints when pathological latencies happen.
--
Philippe.
^ permalink raw reply [flat|nested] 2+ messages in thread
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2010-01-08 10:14 [Xenomai-core] Latency spots due to involuntary mode switches to secondary mode Gilles Chanteperdrix
2010-01-17 21:56 ` Philippe Gerum
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