From: Ravikiran G Thirumalai <kiran@scalex86.org>
To: Eric Dumazet <dada1@cosmosbay.com>
Cc: Andrew Morton <akpm@osdl.org>,
linux-kernel@vger.kernel.org, dipankar@in.ibm.com,
bharata@in.ibm.com, shai@scalex86.org,
Rusty Russell <rusty@rustcorp.com.au>,
netdev@vger.kernel.org, davem@davemloft.net
Subject: Re: [patch 7/11] net: Use bigrefs for net_device.refcount
Date: Tue, 13 Sep 2005 11:53:48 -0700 [thread overview]
Message-ID: <20050913185348.GA3724@localhost.localdomain> (raw)
In-Reply-To: <43271A28.9090301@cosmosbay.com>
On Tue, Sep 13, 2005 at 08:27:52PM +0200, Eric Dumazet wrote:
> Ravikiran G Thirumalai a écrit :
>
> Hum...
>
> Did you tried to place refcnt/netdev_refcnt in a separate cache line than
> queue_lock ? I got good results too...
>
> > /* device queue lock */
> > spinlock_t queue_lock;
> > /* Number of references to this device */
> > - atomic_t refcnt;
> > + struct bigref netdev_refcnt ____cacheline_aligned_in_smp ;
> > /* delayed register/unregister */
> > struct list_head todo_list;
> > /* device name hash chain */
>
> Every time a cpu take the queue_lock spinlock, it exclusively gets one
> cache line. If another cpu try to access netdev_refcnt, it has to grab this
> cache line (even if properely per_cpu designed, there is still one shared
> field). In fact the whole struct net_device should be re-ordered for
> SMP/NUMA performance.
I agree. Maybe placing the queue_lock in a different cacheline is the
right approach?
Thanks,
Kiran
next prev parent reply other threads:[~2005-09-13 18:53 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <20050913155112.GB3570@localhost.localdomain>
2005-09-13 16:10 ` [patch 7/11] net: Use bigrefs for net_device.refcount Ravikiran G Thirumalai
2005-09-13 16:26 ` Stephen Hemminger
2005-09-13 16:35 ` Ben Greear
2005-09-13 16:46 ` Stephen Hemminger
2005-09-13 20:26 ` David S. Miller
2005-09-13 22:16 ` Ravikiran G Thirumalai
2005-09-13 18:27 ` Eric Dumazet
2005-09-13 18:53 ` Ravikiran G Thirumalai [this message]
2005-09-13 16:12 ` [patch 8/11] net: dst_abstraction macros Ravikiran G Thirumalai
2005-09-13 16:17 ` [patch 9/11] net: dst_entry.refcount, use, lastuse to use alloc_percpu Ravikiran G Thirumalai
2005-09-13 20:24 ` David S. Miller
2005-09-13 22:07 ` Ravikiran G Thirumalai
2005-09-13 22:12 ` David S. Miller
2005-09-13 23:17 ` Ravikiran G Thirumalai
2005-09-13 23:27 ` David S. Miller
2005-09-14 7:21 ` Rusty Russell
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