Re: [PATCH 10/10] mm: per device dirty threshold

From: Peter Zijlstra
Date: Sat Apr 21 2007 - 08:17:22 EST



> > > +/*
> > > + * maximal error of a stat counter.
> > > + */
> > > +static inline unsigned long bdi_stat_delta(void)
> > > +{
> > > +#ifdef CONFIG_SMP
> > > + return NR_CPUS * FBC_BATCH;
> >
> > This is enormously wrong for CONFIG_NR_CPUS=1024 on a 2-way.

Right, I knew about that but, uhm.

I wanted to make that num_online_cpus(), and install a hotplug notifier
to fold the percpu delta back into the total on cpu offline.

But I have to look into doing that hotplug notifier stuff.

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