Re: [PATCH]mmap: add alignment for some variables

[Andrew Morton]

On Wed, 30 Mar 2011 09:01:22 +0800 Shaohua Li <shaohua.li@xxxxxxxxx> wrote:

> +/*
> + * Make sure vm_committed_as in one cacheline and not cacheline shared with
> + * other variables. It can be updated by several CPUs frequently.
> + */
> +struct percpu_counter vm_committed_as ____cacheline_internodealigned_in_smp;

The mystery deepens.  The only cross-cpu writeable fields in there are
percpu_counter.lock and its companion percpu_counter.count.  If CPUs
are contending for the lock then that itself is a problem - how does
adding some padding to the struct help anything?

--
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/