From: Asias He <asias@redhat.com>
To: Jens Axboe <axboe@kernel.dk>
Cc: Tejun Heo <tj@kernel.org>, Tim Gardner <rtg.canonical@gmail.com>,
linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
tim.gardner@canonical.com
Subject: Re: [PATCH V3] block: Mitigate lock unbalance caused by lock switching
Date: Wed, 06 Jun 2012 10:12:43 +0800 [thread overview]
Message-ID: <4FCEBC9B.5040201@redhat.com> (raw)
In-Reply-To: <4FC88BF9.2030807@kernel.dk>
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
prev parent reply other threads:[~2012-06-06 2:11 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-05-25 2:10 [PATCH] block: Fix lock unbalance caused by lock disconnect Asias He
2012-05-28 0:07 ` Tejun Heo
2012-05-28 2:15 ` Asias He
2012-05-28 10:20 ` Tejun Heo
2012-05-29 1:49 ` Asias He
2012-06-01 9:28 ` Michael S. Tsirkin
2012-05-28 2:20 ` [PATCH v2] block: Mitigate " Asias He
2012-05-28 10:22 ` Tejun Heo
2012-05-29 1:39 ` [PATCH V3] block: Mitigate lock unbalance caused by lock switching Asias He
2012-05-29 1:39 ` [PATCH] " Asias He
2012-05-29 1:41 ` [PATCH V3] " Tejun Heo
2012-05-29 13:45 ` Tim Gardner
2012-05-30 6:28 ` Asias He
2012-05-30 6:28 ` Tejun Heo
2012-05-30 6:50 ` Asias He
2012-06-01 9:31 ` Jens Axboe
2012-06-06 2:12 ` Asias He [this message]
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