Re: [PATCH V3] block: Mitigate lock unbalance caused by lock switching

[Asias He]

Hello, Jens

On 06/01/2012 05:31 PM, Jens Axboe wrote:
> On 05/30/2012 08:28 AM, Tejun Heo wrote:
> > Hello,
> >
> > On Wed, May 30, 2012 at 3:28 PM, Asias He<asias@xxxxxxxxxx>  wrote:
> > > > Isn't the 'if' clause superfluous ? You could just do the assignment,
> > > > e.g.,
> > > >
> > > > +       spin_lock_irq(lock);
> > > > +       q->queue_lock =&q->__queue_lock;
> > > > +       spin_unlock_irq(lock);
> > >
> > >
> > > Well, this saves a if clause but adds an unnecessary assignment if the lock
> > > is already internal lock.
> >
> > It's not hot path. Dirtying the cacheline there doesn't mean anything.
> > I don't really care either way but making optimization argument is
> > pretty silly here.
>
> And more importantly, dropping the if loses information as well. That's
> a lot more important than any misguided optimization attempts. So I
> agree, the if stays.

Could you pick this patch in your tree?

--
Asias
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