Re: [PATCH] percpu_counter : add percpu_counter_add_fast()

[Andrew Morton]

On Thu, 21 Oct 2010 18:10:13 -0500 (CDT) Christoph Lameter <cl@xxxxxxxxx> wrote:

> On Thu, 21 Oct 2010, Andrew Morton wrote:
> 
> > That isn't actually what I was suggesting.  I was suggesting the use of
> > an inlined, this_cpu_add()-using percpu_counter_add() variant which
> > still does the batched spilling into ->count.  IOW, just speed up the
> > current implementation along the lines of
> >
> > {
> > 	val = this_cpu_add_return(*fbc->counters, amount);
> 
> this_cpu_add_return() is not in the kernel but could be realized using a
> variant offshoot of cmpxchg_local. I had something like that initially but
> omitted it since there was no use case.

this_cpu_add_return() isn't really needed in this application.

{
	this_cpu_add(*fbc->counters, amount);
	if (unlikely(abs(this_cpu_read(*fbc->counters)) > fbc->batch))
		out_of_line_stuff();
}	

will work just fine.				
--
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/