Re: RT patch acceptance

From: Nick Piggin
Date: Tue May 24 2005 - 03:37:53 EST


Ingo Molnar wrote:
* Nick Piggin <nickpiggin@xxxxxxxxxxxx> 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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