Messages in this thread | | | Date | Wed, 06 Jun 2012 10:12:43 +0800 | From | Asias He <> | Subject | Re: [PATCH V3] block: Mitigate lock unbalance caused by lock switching |
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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@redhat.com> 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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