Re: [PATCH -mm]percpu_rw_semaphore-reimplement-to-not-block-the-readers-unnecessarily.fix

[Oleg Nesterov]

On 11/16, Andrew Morton wrote:
>
> On Sun, 11 Nov 2012 19:27:44 +0100
> Oleg Nesterov <oleg@xxxxxxxxxx> wrote:
>
> >  lib/percpu-rwsem.c |   35 +++++++++++++++++++++++++++++++++--
>
> y'know, this looks like a great pile of useless bloat for single-CPU
> machines.  Maybe add a CONFIG_SMP=n variant which simply calls the
> regular rwsem operations?

Yes, I thought about this and probably I'll send the patch...

But note that the regular down_read() won't be actually faster if
there is no writer, and it doesn't allow to add other features.

I'll try to think, perhaps it would be enough to add a couple of
"ifdef CONFIG_SMP" into this code, say, to avoid __percpu.

Oleg.

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