Re: [patch 0/4] ide: Break ide_lock to per-hwgroup lock

[Bartlomiej Zolnierkiewicz]

On 9/7/05, Jens Axboe <axboe@xxxxxxx> wrote:
> On Wed, Sep 07 2005, Ravikiran G Thirumalai wrote:
> > On Wed, Sep 07, 2005 at 11:19:24AM +0200, Jens Axboe wrote:
> > > On Tue, Sep 06 2005, Ravikiran G Thirumalai wrote:
> > > > The following patchset breaks down the global ide_lock to per-hwgroup lock.
> > > > We have taken the following approach.
> > >
> > > Curious, what is the point of this?
> > >
> >
> > On smp machines with multiple ide interfaces, we take per-group lock instead
> > of a global lock, there by breaking the lock to per-irq hwgroups.
>
> I realize the theory behind breaking up locks, I'm just wondering about
> this specific case. Please show actual contention data promoting this
> specific case, we don't break up locks "just because".
>
> I'm asking because I've never heard anyone complain about IDE lock
> contention and a proper patch usually comes with analysis of why it is
> needed.

Since ide_lock spinlock is used for all drives as queue lock and for all
controllers as IDE lock I guess that with multiple controllers there is a lot
contention on it...

Breaking ide_lock is fine with me however seeing numbers would
greatly help in getting wider acceptance for this change, Ravikiran?

Bartlomiej
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