netdev - Re: [PATCH] skbuff: make skb_put

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Date:   Fri, 16 Jun 2017 00:17:25 +0200
From:   Johannes Berg <johannes@...solutions.net>
To:     Joe Perches <joe@...ches.com>, netdev@...r.kernel.org
Subject: Re: [PATCH] skbuff: make skb_put_zero() return void

On Wed, 2017-06-14 at 14:18 -0700, Joe Perches wrote:
> On Wed, 2017-06-14 at 22:40 +0200, Johannes Berg wrote:
> > On Wed, 2017-06-14 at 13:36 -0700, Joe Perches wrote:
> > > 
> > > Given you are adding a lot of these, it might be better
> > > to add an exported function that duplicates most of
> > > skb_put with a memset at the end.
> > 
> > Yeah, could be done. I'm not sure why you'd want to duplicate it
> > rather
> > than call it though? To make it about as fast?
> 
> Yeah, that and reduced stack use.
> 
> Dunno how performance sensitive these uses really are
> but it seems some might be for slow cpu wireless APs in
> both the rx and tx paths.

I haven't really checked now, but the wireless (mac80211) ones I saw
weren't in the data TX/RX, only for management SKBs which are pretty
much a slowpath.

Anyway, I guess you know how to propose a patch with this :-)

However, I think in that case there should be something like
skb_pull_inline, so that the skb_put code here isn't all copied around,
but just lives in a single place that gets inlined into skb_put() and
skb_put_zero().

johannes