From: Eric Dumazet <eric.dumazet@gmail.com>
To: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: David Miller <davem@davemloft.net>,
mingo@elte.hu, paulmck@linux.vnet.ibm.com,
cl@linux-foundation.org, penberg@kernel.org, mpm@selenic.com,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
netdev@vger.kernel.org
Subject: Re: [PATCH 4/4 V2] net,rcu: don't assume the size of struct rcu_head
Date: Wed, 02 Mar 2011 04:02:05 +0100 [thread overview]
Message-ID: <1299034925.2930.52.camel@edumazet-laptop> (raw)
In-Reply-To: <4D6DAF86.2000407@cn.fujitsu.com>
Le mercredi 02 mars 2011 A 10:46 +0800, Lai Jiangshan a A(C)crit :
> Is it the cause of false sharing? I thought that all are rare write(except __refcnt)
> since it is protected by RCU.
>
> Do you allow me just move the seldom access rcu_head to the end of the structure
> and add pads before __refcnt? I guess it increases about 3% the size of dst_entry.
dst_entry is a base class.
Its included at the beginning of other structs.
Moving rcu_head "at the end" just move it right in the middle of upper
objects as a matter of fact. This might add one cache line miss on
critical network object. A complete audit is needed.
David is doing some changes in this area, so things move fast anyway.
> I accept that I leave this code as is, when I change rcu_head I will
notify you.
>
Thanks
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next prev parent reply other threads:[~2011-03-02 3:02 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-03-01 8:03 [PATCH 4/4] " Lai Jiangshan
2011-03-01 8:16 ` David Miller
2011-03-01 8:20 ` Eric Dumazet
2011-03-01 8:53 ` [PATCH 4/4 V2] " Lai Jiangshan
2011-03-01 9:20 ` Eric Dumazet
2011-03-02 2:46 ` Lai Jiangshan
2011-03-02 3:02 ` Eric Dumazet [this message]
2011-03-01 8:20 ` [PATCH 4/4] " Eric Dumazet
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