netdev - Re: [PATCH v2 net-next 4/4] tcp: implement coalescing on backlog queue

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Message-ID: <bd893266-ecc5-9968-dc07-d52ff6b46df7@gmail.com>
Date:   Tue, 27 Nov 2018 14:13:00 -0800
From:   Eric Dumazet <eric.dumazet@...il.com>
To:     Neal Cardwell <ncardwell@...gle.com>,
        Eric Dumazet <edumazet@...gle.com>
Cc:     David Miller <davem@...emloft.net>,
        Netdev <netdev@...r.kernel.org>, jean-louis@...ond.be,
        Yuchung Cheng <ycheng@...gle.com>,
        Eric Dumazet <eric.dumazet@...il.com>
Subject: Re: [PATCH v2 net-next 4/4] tcp: implement coalescing on backlog
 queue



On 11/27/2018 01:58 PM, Neal Cardwell wrote:

> I wonder if technically perhaps the logic should skip coalescing if
> the tail or skb has the TCP_FLAG_URG bit set? It seems if skbs are
> coalesced, and some have urgent data and some do not, then the
> TCP_FLAG_URG bit will be accumulated into the tail header, but there
> will be no way to ensure the correct urgent offsets for the one or
> more skbs with urgent data are passed along.

Yes, I guess I need to fix that, thanks.

I will simply make sure both thtail->urg and th->urg are not set.

I could only test thtail->urg, but that would require copying th->urg_ptr and th->urg,
and quite frankly we should not spend cycles on URG stuff.