Re: [net-next] tcp: allow drivers to tweak TSQ logic

From: Johannes Berg <johannes@sipsolutions.net>
To: Eric Dumazet <eric.dumazet@gmail.com>,
	David Miller <davem@davemloft.net>
Cc: netdev <netdev@vger.kernel.org>,
	"Toke Høiland-Jørgensen" <toke@toke.dk>,
	"Kir Kolyshkin" <kir@openvz.org>
Subject: Re: [net-next] tcp: allow drivers to tweak TSQ logic
Date: Sat, 11 Nov 2017 15:27:19 +0100	[thread overview]
Message-ID: <1510410439.12037.10.camel@sipsolutions.net> (raw)
In-Reply-To: <1510281664.2849.143.camel@edumazet-glaptop3.roam.corp.google.com>

Thanks Eric!

> We expect wifi drivers to set this field to smaller values (tests have
> been done with values from 6 to 9)

I suppose we should test each driver or so.

> They would have to use following template :
> 
> if (skb->sk && skb->sk->sk_pacing_shift != MY_PACING_SHIFT)
>      skb->sk->sk_pacing_shift = MY_PACING_SHIFT;

Hm. I wish we wouldn't have to do this on every skb, but perhaps it
doesn't matter that much.

>  	u16			sk_gso_max_segs;
> +	u8			sk_pacing_shift;

I guess you tried to fill a hole, but weren't we saying that it would
be better in the same cacheline? Then again, perhaps both cachelines
are resident anyway, haven't looked at this now.

Unrelated to that, I think this is missing a documentation update since
the struct has kernel-doc comments.

johannes