From: "Nikita V. Youshchenko" <yoush@cs.msu.su>
To: dmarkh@cfl.rr.com
Cc: Vladimir Cotfas <vladc@mantatest.com>,
linux-rt-users@vger.kernel.org,
Scott Gilbertson <scottg@mantatest.com>
Subject: Re: Latency Problems with 2.6.31/PREEMPT_RT on a 1.2GHz Celeron
Date: Mon, 21 Dec 2009 12:16:19 +0300 [thread overview]
Message-ID: <200912211216.20588@zigzag.lvk.cs.msu.su> (raw)
In-Reply-To: <4B2CBA28.1030405@cfl.rr.com>
> On 12/18/2009 11:56 AM, Vladimir Cotfas wrote:
> > All,
> >
> > I have a a driver that must process an interrupt every 100 uS without
> > missing any. I am having latency issues and I am looking for some help
> > debugging my problem.
>
> You'll probably never get this working reliably with the RT kernel.
> Latencies are more deterministic with the RT kernel but slightly higher.
> You'll have better luck with a vanilla kernel running your app in run
> level 4. And then even better luck running on an SMP machine isolating
> your process and IRQ to a single processor. And stay away from the VGA
> console. You have better luck with faster hardware too.
We have seen <20us avg latencies on RT kernel on slower powerpc-based SoC.
The only problem is that sometimes we got single-shot latency >150 us -
that happened when sched tick was running for >100 us with interrupts
disabled.
next prev parent reply other threads:[~2009-12-21 9:16 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <abe060d60912171537j10fe194r5f0cd1aca85475df@mail.gmail.com>
2009-12-18 16:56 ` Latency Problems with 2.6.31/PREEMPT_RT on a 1.2GHz Celeron Vladimir Cotfas
2009-12-19 11:34 ` Mark Hounschell
2009-12-21 9:16 ` Nikita V. Youshchenko [this message]
2009-12-21 10:05 ` Mark Hounschell
2009-12-21 20:36 ` Carsten Emde
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