Re: [PATCH]O18.1int

[Nick Piggin]

Guillaume Chazarain wrote:

> 28/08/03 14:34:15, Nick Piggin <piggin@xxxxxxxxxxxxxxx> wrote:
>
> > Guillaume Chazarain wrote:
> >
> >
> > > Hi Con (and linux-kernel),
> > >
> > > I noticed a regression wrt 2.6.0-test4 and 2.4.22 with this
> > > big context-switcher:
> > Hi Guillaume,
> > If you get the time, would you be able to try my patch? Thanks.
>
> Here are the results for Nick's v8:
>
> top(1):
>
>  639 g         30   0  1336  260 1308 R 51.2  0.1   0:03.80 a.out
>  638 g         22   0  1336  260 1308 S 47.3  0.1   0:03.39 a.out
>
> User time (seconds): 0.57
> System time (seconds): 2.72
> Elapsed (wall clock) time (h:mm:ss or m:ss): 0:06.85
> Minor (reclaiming a frame) page faults: 17

Thanks Guillaume, so not very good. Its interesting that there can
be such a big difference in performance, but its a very simple app
so makes a good test for the specific regression.

In both Con's and my patches, the reader gets a bit more CPU. This
might be due to it preempting the writer more often on wakeups,
which would lead to more scheduling per work done and a regression.

If this is the case, I'm not sure the behaviour is too undesirable
though: its often very important for woken processes to be run
quickly. Its not clear that this workload is something we would
want to optimize for. Assuming the problem is what I guess.

I will take a look into it further when I get time tomorrow.


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