Re: [PATCH v10 03/35] dcache: convert dentry_stat.nr_unused to per-cpu counters

Andrew Morton
2013-06-06T22:25:46Z

On Thu, 6 Jun 2013 16:40:42 +0400 Glauber Costa <glommer@parallels.com> wrote:

> +/*
> + * Here we resort to our own counters instead of using generic per-cpu counters
> + * for consistency with what the vfs inode code does. We are expected to harvest
> + * better code and performance by having our own specialized counters.
> + *
> + * Please note that the loop is done over all possible CPUs, not over all online
> + * CPUs. The reason for this is that we don't want to play games with CPUs going
> + * on and off. If one of them goes off, we will just keep their counters.
> + *
> + * glommer: See cffbc8a for details, and if you ever intend to change this,
> + * please update all vfs counters to match.

Handling CPU hotplug is really quite simple - see lib/percpu_counter.c

(I can't imagine why percpu_counter_hotcpu_callback() sums all the
counters - all it needs to do is to spill hcpu's counter into current's
counter).

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