Re: [PATCH 2/2] block: Convert BDI proportion calculations toflexible proportions

[Peter Zijlstra]

On Tue, 2012-05-15 at 17:43 +0200, Jan Kara wrote:
> +static struct timer_list writeout_period_timer =
> +               TIMER_DEFERRED_INITIALIZER(writeout_period, 0, 0); 

So the problem with using a deferred timer is that it 'ignores' idle
time. So if a very busy period is followed by a real quiet period you'd
expect all the proportions to have aged to 0, but they won't have.

One way to solve that is to track a jiffies count of the last time the
timer triggered and compute the missed periods from that and extend
fprop_new_period() to deal with period increments of more than 1.

The other is of course to not use deferred timers.
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/