Mark Hahn wrote:
> > bigger thing for Alpha than for Intel). On our newer systems we fully expect
> > hundreds, if not thousands, of tasks. The more commercially accepted Linux
>
> the issue is *runnable* tasks. do your machines routinely report
> loadaverages of 1000? if so, I'm impressed!
>
Yes, I did get that. :) And yes, they do routinely report such load averages. As
a matter of fact, I was just stress-testing a system and when I looked the load
average was 2002. Granted the test I was running (AIM) is artificial (all tests
of its ilk are), it was designed as a representative measure of system
performance. Representative in that it represents what systems actually do.
Do we here have systems with that high a load average from actual use? No - but
we're not running any massive databases or web servers either. Do I have hard
proof that our customers do that? I doubt anyone would tell me if they did anyway
;)
Point is, it's possible, and it's becoming more and more probable every day. (I
had a co-worker testing a system and he gave up at a load average of somewhere
around 16000 because he didn't want to wait any longer.) Remember - this is the
age of server consolidation - more stuff on fewer systems. Lots of little piddly
things on tiny boxen scattered here there and everywhere was the NT way and it has
proven to not work (on a large scale at the very least).
>
> the issue here is whether someone can come up with a maintainable
> scheduler that has the requisite performance. since the runqueue is
> normally short, the scheduler's performance function must have a
> very small constant term. if it's true that there are applications
> that result in long runqueues, then the performance curve needs to
> be as flat and horizontal as possible, again, without degrading the
> constant term.
>
Agreed. That's one of the reasons that Tru64 has a per-cpu runqueue backed by a
global runqueue (I believe everyone that cares to would know that, so I think
I can say that ;). I know such an idea is never going to make it into Linux, but
it's in the direction we should be looking. I haven't looked at the scheduler
lately... maybe I should again...hmm...
>
> AFAIK, loopback volanomark does not resemble _any_ real application.
>
No, probably not technically. It just means that they didn't have to configure a
big system with a whole bunch of clients and enough bandwidth to put the same type
of load on the system. With the advent of multi-hundred MB/s plus Internet
connections and massive Intranet requirements, such bandwidth isn't impossible to
imagine.
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This archive was generated by hypermail 2b29 : Sun Jan 23 2000 - 21:00:22 EST