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SubjectRe: [patch 7/11] net: Use bigrefs for net_device.refcount
Stephen Hemminger wrote:
> On Tue, 13 Sep 2005 09:10:12 -0700
> Ravikiran G Thirumalai <kiran@scalex86.org> wrote:
>
>
>>The net_device has a refcnt used to keep track of it's uses.
>>This is used at the time of unregistering the network device
>>(module unloading ..) (see netdev_wait_allrefs) .
>>For loopback_dev , this refcnt increment/decrement is causing
>>unnecessary traffic on the interlink for NUMA system
>>affecting it's performance. This patch improves tbench numbers by 6% on a
>>8way x86 Xeon (x445).
>>
>
>
> Since when is bringing a network device up/down performance critical?

We grab and drop a reference for each poll of a device, roughly.

See dev_hold in _netif_rx_schedule(struct net_device *dev)
in include/netdevice.h, for instance.

Thanks,
Ben

--
Ben Greear <greearb@candelatech.com>
Candela Technologies Inc http://www.candelatech.com

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