Subject: Re: RT patch acceptance
From: Daniel Walker <dwalker@mvista.com>
Reply-To: dwalker@mvista.com
To: Ingo Molnar <mingo@elte.hu>
Cc: Nick Piggin <nickpiggin@yahoo.com.au>,
       Christoph Hellwig <hch@infradead.org>, linux-kernel@vger.kernel.org,
       akpm@osdl.org, sdietrich@mvista.com
In-Reply-To: <20050524081517.GA22205@elte.hu>
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Organization: MontaVista
Date: Tue, 24 May 2005 11:01:30 -0700
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On Tue, 2005-05-24 at 10:15 +0200, Ingo Molnar wrote:
> * Nick Piggin <nickpiggin@yahoo.com.au> wrote:
> 
> > Of course this is weighed off against the improvements added to the
> > kernel. I'm personally not too clear on what those improvements are; a
> > bit better soft-realtime response? (I don't know) [...]
> 
> what the -RT kernel (PREEMPT_RT) offers are guaranteed hard-realtime 
> responses. ~15 usecs worst-case latency on a 2GHz Athlon64. On arbitrary 
> (SCHED_OTHER) workloads. (I.e. i've measured such worst-case latencies 
> when running 1000 hackbench tasks or when swapping the box to death, or 
> when running 40 parallel copies of the LTP testsuite.)


I wouldn't start making guarantees yet .. For instance printk can hold
off interrupts for unknown periods (unknown to me anyway) depending on
the size of the strings that it prints.

Daniel

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