From: Nick Piggin <nickpiggin@yahoo.com.au>
To: Corey Minyard <minyard@acm.org>
Cc: Arjan van de Ven <arjan@infradead.org>, Greg KH <greg@kroah.com>,
Sergey Vlasov <vsu@altlinux.ru>,
lkml <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH] New operation for kref to help avoid locks
Date: Wed, 02 Mar 2005 11:02:33 +1100 [thread overview]
Message-ID: <42250299.8080709@yahoo.com.au> (raw)
In-Reply-To: <4224FC33.6040405@acm.org>
Corey Minyard wrote:
> Arjan van de Ven wrote:
>
>>> Just doing an atomic operation is not faster than doing a lock, an
>>> atomic operation, then an unlock? Am I missing something?
>>>
>>
>>
>> if the lock and the atomic are on the same cacheline they're the same
>> cost on most modern cpus...
>>
>>
> Ah, I see. Not likely to ever be the case with this. The lock will
> likely be with the main data structure (the list, or whatever) and the
> refcount will be in the individual item in the main data structure (list
> entry).
>
Is get_with_check actually going to be useful for anything? It
seems like it promotes complex and potentially unsafe schemes.
eg. In your queue example, it would usually be better to have
a refcount for being on queue, and entry_completed would remove
the entry from the queue and accordingly drop the refcount. The
release function would then just free it.
next prev parent reply other threads:[~2005-03-02 0:02 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2005-02-26 15:55 [PATCH] New operation for kref to help avoid locks Corey Minyard
2005-02-26 20:20 ` Sergey Vlasov
2005-02-26 22:23 ` Corey Minyard
2005-03-01 20:15 ` Greg KH
2005-03-01 21:02 ` Arjan van de Ven
2005-03-01 21:24 ` Greg KH
2005-03-01 21:54 ` Corey Minyard
2005-03-01 22:14 ` Arjan van de Ven
2005-03-01 23:35 ` Corey Minyard
2005-03-02 0:02 ` Nick Piggin [this message]
2005-03-02 0:28 ` Corey Minyard
2005-03-02 0:34 ` Nick Piggin
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