Re: [PATCH 2/5] vmevent: Convert from deferred timer to deferred work

[Anton Vorontsov <anton.vorontsov@linaro.org>]

On Fri, Jun 08, 2012 at 10:03:24AM +0300, Pekka Enberg wrote:
> On Fri, Jun 8, 2012 at 9:58 AM, Anton Vorontsov
> <anton.vorontsov@linaro.org> wrote:
> > If you're saying that we should set up a timer in the userland and
> > constantly read /proc/vmstat, then we will cause CPU wake up
> > every 100ms, which is not acceptable. Well, we can try to introduce
> > deferrable timers for the userspace. But then it would still add
> > a lot more overhead for our task, as this solution adds other two
> > context switches to read and parse /proc/vmstat. I guess this is
> > not a show-stopper though, so we can discuss this.
> >
> > Leonid, Pekka, what do you think about the idea?
> 
> That's exactly the kind of half-assed ABI that lead to people
> inventing out-of-tree lowmem notifiers in the first place.

:-)

Well, at least powersaving-wise, the solution w/ userland deferred
timers would be much better then just looping over /proc/vmstat each
100ms, and it is comparable to vmevent. Not pretty, but still would
work.

> I'd be more interested to know what people think of Minchan's that
> gets rid of vmstat sampling.

I answered to Minchan's post. The thing is that Minchan's idea
is not a substitution for vmevent. To me it seems like a shrinker w/
some pre-filter.

Thanks,

-- 
Anton Vorontsov
Email: cbouatmailru@gmail.com

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