From: Philippe Gerum <rpm@xenomai.org>
To: Jan Kiszka <jan.kiszka@domain.hid>
Cc: xenomai-core <xenomai@xenomai.org>
Subject: Re: [Xenomai-core] timer optimisations
Date: Mon, 22 May 2006 11:48:41 +0200 [thread overview]
Message-ID: <447188F9.60905@domain.hid> (raw)
In-Reply-To: <44717FBA.1030207@domain.hid>
Jan Kiszka wrote:
> Hi,
>
> while I originally only wanted to add timer abstraction to RTDM, I now
> have patch series for xntimer pending on my box pushing this layer
> closer to hrtimer.
>
> But before posting it for discussion (needs further testing anyway), I
> have two questions regarding some minor though not totally uninteresting
> optimisation possibilities:
>
> 1. Is calling xntimer_start() with value=XN_INFINITE a real use case?
> It's not documented explicitly. The effect of such an invocation
> looks a bit like xntimer_stop(), but I didn't find a real caller so
> far to asses it's relevance.
xnpod_start_timer() uses this property to start the host tick relay
timer. If XNARCH_HOST_TICK is zero, then no relay is required, and the
timer should remain passive.
>
> If it is not used and could rather be declared illegal, we could safe
> the related code in the do_timer_start handlers.
>
Dunno. To do that, we would need to carefully inspect each and every
caller, especially for the various skins, which implies to analyze the
requirements of the mimicked API too.
> 2. rthal_timer_program_shot() uses explicit rthal_local_irq_save_hw on
> ia64 and i386. Given the head optimisation, IRQs should already be
> disabled when calling this service. So, can this IRQ masking be made
> depending on !CONFIG_XENO_OPT_PIPELINE_HEAD?
>
Yes.
> ARM uses an additional lock as well, but it's hidden inside the ipipe
> patch and is likely required to remain independent of the caller's
> properties.
>
> Jan
>
>
>
> ------------------------------------------------------------------------
>
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> Xenomai-core@domain.hid
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--
Philippe.
next prev parent reply other threads:[~2006-05-22 9:48 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-05-22 9:09 [Xenomai-core] timer optimisations Jan Kiszka
2006-05-22 9:48 ` Philippe Gerum [this message]
2006-05-22 10:46 ` Jan Kiszka
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