Re: [dm-devel] DM-CRYPT: Scale to multiple CPUs v3

[Alasdair G Kergon <agk redhat com>]

> > AFAIK Nested dm-crypt is not extreme for some folk who have routine
> > configurations using it.  But if in_interrupt is set how does this code
                                     ^^^^^^^^^^^
> > work for them now compared to how it worked before?

On Sun, Oct 10, 2010 at 08:51:00PM +0200, Andi Kleen wrote:
> Previously they will all pile up on the single worker thread.
> Now in the nested case the nested work is run in their own
> context. This should actually scale better because you
> get parallelism too, not contention on a single resource.
 
Not if in_interrupt is set though?
+       if (per_cpu(io_wq_cpu, cpu) == current && !in_interrupt()) {

What I am missing here?

(And assume there is only 1 CPU too for worst case behaviour, presumably.)

Alasdair