Re: [patch 7/11] net: Use bigrefs for net_device.refcount

[Ben Greear]

Stephen Hemminger wrote:
> On Tue, 13 Sep 2005 09:10:12 -0700
> Ravikiran G Thirumalai <kiran@xxxxxxxxxxxx> 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@xxxxxxxxxxxxxxx>
Candela Technologies Inc  http://www.candelatech.com

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