netdev - Re: [PATCH net-next 3/3] tcp: implement head drops in backlog queue

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Date:   Wed, 21 Nov 2018 16:54:52 -0800
From:   Yuchung Cheng <ycheng@...gle.com>
To:     Eric Dumazet <edumazet@...gle.com>
Cc:     Eric Dumazet <eric.dumazet@...il.com>,
        David Miller <davem@...emloft.net>,
        netdev <netdev@...r.kernel.org>,
        Jean-Louis Dupond <jean-louis@...ond.be>,
        Neal Cardwell <ncardwell@...gle.com>
Subject: Re: [PATCH net-next 3/3] tcp: implement head drops in backlog queue

On Wed, Nov 21, 2018 at 4:18 PM, Eric Dumazet <edumazet@...gle.com> wrote:
> On Wed, Nov 21, 2018 at 3:52 PM Eric Dumazet <edumazet@...gle.com> wrote:
>> This is basically what the patch does, the while loop breaks when we have freed
>> just enough skbs.
>
> Also this is the patch we tested with Jean-Louis on his host, bring
> very nice results,
> even from an old stack sender (the one that had problems with the SACK
> compression we just fixed)
>
> Keep in mind we are dealing here with the exception, I would not spend
> too much time
> testing another variant if this one simply works.
To clarify I do think this patch set is overall useful so I only
wanted to discuss the specifics of the head drop.

It occurs to me we check the limit differently (one w/ 64KB more), so
we may overcommit and trim more often than necessary?