Re: Multi-device update

[Jens Axboe <jens.axboe@oracle.com>]

On Wed, Apr 16 2008, Andi Kleen wrote:
> Chris Mason wrote:
> > On Wednesday 16 April 2008, Andi Kleen wrote:
> >> Chris Mason <chris.mason@oracle.com> writes:
> >>> On Wednesday 16 April 2008, Andi Kleen wrote:
> >>>> Chris Mason <chris.mason@oracle.com> writes:
> >>>>> The async work queues include code to checksum data pages without the
> >>>>> FS mutex
> >>>> Are they able to distribute work to other cores?
> >>> Yes, it just uses a workqueue.
> >> Unfortunately work queues don't do that by default currently. They
> >> tend to process on the current CPU only.
> > 
> > Well, I see multiple work queue threads using CPU time, but I haven't spent 
> > much time optimizing it.  There's definitely room for improvement.
> 
> That's likely because you submit from multiple CPUs. But with a single
> submitter running on a single CPU there shouldn't be any load balancing
> currently.

There have been various implementations of queue_work_on() posted
through the years, I've had one version that I've used off and on for a
long time:

http://git.kernel.dk/?p=linux-2.6-block.git;a=commit;h=c68c42fd6df96f5b3fb5b8b47c571f233d054c71

then you need some balancing decider on top of that, of course.

-- 
Jens Axboe