Re: speed difference between using hard-linked and modular drives?

Rusty Russell
2001-11-09T05:11:56Z

On 09 Nov 2001 00:00:19 +0100
Andi Kleen <ak@suse.de> wrote:

> Ingo Molnar <mingo@elte.hu> writes:
> >
> > we should fix this by trying to allocate continuous physical memory if
> > possible, and fall back to vmalloc() only if this allocation fails.
>
> Check -aa. A patch to do that has been in there for some time now.
>
> -Andi
>
> P.S.: It makes a measurable difference with some Oracle benchmarks with
> the Qlogic driver.

Modules have lots of little disadvantages that add up. The speed penalty
on various platforms is one, the load/unload race complexity is another.

There's a widespread "modules are free!" mentality: they're not, and we
can add complexity trying to make them "free", but it might be wiser to
realize that dynamic adding and deleting from a running kernel is a
problem on par with a pagagble kernel, and may not be the greatest thing
since sliced bread.

Rusty.