On Wed, 29 Oct 2014, Peter Zijlstra wrote:
> On Wed, Oct 29, 2014 at 09:23:42PM +0100, Thomas Gleixner wrote:
> > But at least it allows to mitigate the impact by making it conditional
> > at a central point.
> >
> > static inline void netpoll_lock(struct net_device *nd)
> > {
> > if (netpoll_active(nd))
> > spin_lock(&nd->netpoll_lock);
> > }
>
> branch fail vs lock might be a toss on most machines, but if we're
> hitting cold cachelines we loose big.
Well, if the net_device is not cache hot on irq entry you have lost
already. The extra branch/lock is not going to add much to that.
Thanks,
tglx
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