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Date: Wed, 25 Sep 2019 14:25:01 +0200 From: Daniel Borkmann <daniel@...earbox.net> To: xiaolinkui <xiaolinkui@...inos.cn> Cc: davem@...emloft.net, netdev@...r.kernel.org Subject: Re: [PATCH] net: use unlikely for dql_avail case On Wed, Sep 25, 2019 at 10:40:43AM +0800, xiaolinkui wrote: > This is an unlikely case, use unlikely() on it seems logical. > > Signed-off-by: xiaolinkui <xiaolinkui@...inos.cn> It's already here [0], but should probably rather get reverted instead due to lack of a more elaborate reasoning on why it needs to be done this way instead of letting compiler do it's job in this case. "Seems logical" is never a good technical explanation. Do you have any better analysis you performed prior to submitting the patch (twice by now)? Thanks, Daniel [0] https://git.kernel.org/pub/scm/linux/kernel/git/torvalds/linux.git/commit/?id=f3acd33d840d3ea3e1233d234605c85cbbf26054 > --- > include/linux/netdevice.h | 2 +- > 1 file changed, 1 insertion(+), 1 deletion(-) > > diff --git a/include/linux/netdevice.h b/include/linux/netdevice.h > index 88292953aa6f..005f3da1b13d 100644 > --- a/include/linux/netdevice.h > +++ b/include/linux/netdevice.h > @@ -3270,7 +3270,7 @@ static inline void netdev_tx_completed_queue(struct netdev_queue *dev_queue, > */ > smp_mb(); > > - if (dql_avail(&dev_queue->dql) < 0) > + if (unlikely(dql_avail(&dev_queue->dql) < 0)) > return; > > if (test_and_clear_bit(__QUEUE_STATE_STACK_XOFF, &dev_queue->state)) > -- > 2.17.1 > > >
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