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Date: Wed, 30 May 2012 15:28:37 +0900 From: Tejun Heo <tj@...nel.org> To: Asias He <asias@...hat.com> Cc: Tim Gardner <rtg.canonical@...il.com>, Jens Axboe <axboe@...nel.dk>, linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org, tim.gardner@...onical.com Subject: Re: [PATCH V3] block: Mitigate lock unbalance caused by lock switching Hello, On Wed, May 30, 2012 at 3:28 PM, Asias He <asias@...hat.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. -- tejun -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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