Message-ID: <4292E559.3080302@yahoo.com.au>
Date: Tue, 24 May 2005 18:27:05 +1000
From: Nick Piggin <nickpiggin@yahoo.com.au>
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To: Ingo Molnar <mingo@elte.hu>
CC: Christoph Hellwig <hch@infradead.org>, Daniel Walker <dwalker@mvista.com>,
       linux-kernel@vger.kernel.org, akpm@osdl.org, sdietrich@mvista.com
Subject: Re: RT patch acceptance
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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.)
> 

Oh OK, I didn't realise it is aiming for hard RT. Cool! but
that wasn't so much the main point I was trying to make...

> so it's well worth the effort, but there's no hurry and all the changes 
> are incremental anyway. I can understand Daniel's desire for more action 
> (he's got a product to worry about), but upstream isnt ready for this 
> yet.
> 

Basically the same questions I think will still be up for debate.
Not that I want to start now, nor do I really have any feelings
on the matter yet (other than I'm glad you're not in a hurry :)).

For example, it may not be clear to everyone that it is
automatically well worth the effort ;) And others may really
want the functionality but prefer it to be done in a specialised
software like Christoph said.

Nick

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