From: Jarek Poplawski <jarkao2@gmail.com>
To: David Miller <davem@davemloft.net>
Cc: jesse@nicira.com, eric.dumazet@gmail.com, netdev@vger.kernel.org
Subject: Re: [PATCH net-next-2.6] net: inet_add_protocol() can use cmpxchg()
Date: Thu, 9 Sep 2010 06:42:22 +0000 [thread overview]
Message-ID: <20100909064222.GA6951@ff.dom.local> (raw)
In-Reply-To: <20100908.213059.98904271.davem@davemloft.net>
On 2010-09-09 06:30, David Miller wrote:
> From: Jesse Gross <jesse@nicira.com>
> Date: Wed, 8 Sep 2010 16:49:27 -0700
>
>> On Wed, Sep 8, 2010 at 3:56 PM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
>>> Use cmpxchg() to get rid of spinlocks in inet_add_protocol() and
>>> friends.
>>>
>>> inet_protos[] & inet6_protos[] are moved to read_mostly section
>>>
>>> Signed-off-by: Eric Dumazet <eric.dumazet@gmail.com>
>>
>> What's the benefit to this? It's hard to imagine that add/deleting
>> protocols is highly contended. On the other hand, a simple spinlock
>> is very easy to look at and verify correct, while this takes a little
>> more thought.
>
> Smaller data section is the benefit, thus less cache pressure there.
>
Of course, each case is different, but generally I understand Jesse's
concern. Smaller data section argument shouldn't be enough. There is
some reason we do it in C not asm, and there is some cost of
unreadable code too.
Jarek P.
next prev parent reply other threads:[~2010-09-09 6:42 UTC|newest]
Thread overview: 15+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-09-08 22:56 [PATCH net-next-2.6] net: inet_add_protocol() can use cmpxchg() Eric Dumazet
2010-09-08 23:49 ` Jesse Gross
2010-09-09 4:30 ` David Miller
2010-09-09 6:42 ` Jarek Poplawski [this message]
2010-09-09 6:55 ` Eric Dumazet
2010-09-09 7:09 ` Jarek Poplawski
2010-09-09 7:24 ` Jarek Poplawski
2010-09-09 9:08 ` Jarek Poplawski
2010-09-09 9:23 ` Eric Dumazet
2010-09-09 9:42 ` Jarek Poplawski
2010-09-09 9:59 ` Jarek Poplawski
2010-09-09 12:57 ` Eric Dumazet
2010-09-09 15:38 ` Jarek Poplawski
2010-09-09 5:23 ` Eric Dumazet
2010-09-09 4:31 ` David Miller
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