Robert Watson wrote:
On Mon, 8 Nov 2004, Mipam wrote:
Thanks for your reply, okay, then i'd like to enable preemption. I
noticed it's not in the GENERIC kernel config file. So: options
PREEMPTION would suffice to enable it i guess? Any experience with
preemption. noticable changes? So the problem: "PREEMPTION triggers
frequent hangs" is resolved? Btw, is RELENG_5 also stable or only for
early adopters? I really would like to see ule working stable in
combination with preemption, but in 5.3 it won't happen. Maybe ule will
be enabled later in the 5 series?
There was a series of bugs in the scheduler which got tickled by preemption; I'm unclear as to whether they were all resolved before 5.3 or whether they require fixes in HEAD that haven't yet been merged. It may well be safe, but I make no promises. Hopefully we can trick Julian or John into responding to this thread. :-) Having it off by default on 5.3 is certainly the more conservative (and reasonable) position, but if it helps your environment and appears stable, there should be no reason not to turn it on. It should substantially improve latency in interrupt processing as well as packet processing.
I think that PREEMPTION with SCHED_4BSD might be ok..
It's hard to say because it's always harder to prove something correct than to prove it broken :-)
Hopefully with the rush off, we can sit down and try "prove it ok" and take some cleanup passes over it.
I still owe my wife a significant "chunk-o-time" (TM) however so count me out for a while .
Hopefully however ups@ is coming online again this week.
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