From: Eric Dumazet <eric.dumazet@gmail.com>
To: David Miller <davem@davemloft.net>
Cc: rick.jones2@hp.com, netdev@vger.kernel.org, therbert@google.com,
ncardwell@google.com, maze@google.com, ycheng@google.com,
ilpo.jarvinen@helsinki.fi
Subject: Re: [PATCH 2/2 net-next] tcp: sk_add_backlog() is too agressive for TCP
Date: Mon, 23 Apr 2012 22:37:26 +0200 [thread overview]
Message-ID: <1335213446.5205.65.camel@edumazet-glaptop> (raw)
In-Reply-To: <20120423.160149.1515408777176168288.davem@davemloft.net>
On Mon, 2012-04-23 at 16:01 -0400, David Miller wrote:
> Hmmm... why don't we just acknowledge reality and special case ACKs?
>
Yes why not.
> If a TCP packet is dataless we should just let it go through no matter
> what and with no limits. It is by definition transient and will not
> get queued up into the socket past this backlog stage.
>
Even being transient we need a limit. Without copybreak, an ACK can cost
2048+256 bytes.
In my 10Gbit tests (standard netperf using 16K buffers), I've seen
backlogs of 300 ACK packets...
> This proposed patch allows non-dataless packets to eat more space in
> the backlog, thus the concern and slight pushback. And from another
> perspective, having the stack process data packets which will just
> get dropped when we try to attach it to the receive queue is just
> wasted work.
We could try to coalesce ACKs before backlogging them. I'll work on
this.
Thanks
next prev parent reply other threads:[~2012-04-23 20:37 UTC|newest]
Thread overview: 37+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-04-23 9:38 [PATCH 2/2 net-next] tcp: sk_add_backlog() is too agressive for TCP Eric Dumazet
2012-04-23 17:14 ` Rick Jones
2012-04-23 17:23 ` Eric Dumazet
2012-04-23 20:01 ` David Miller
2012-04-23 20:37 ` Eric Dumazet [this message]
2012-04-23 20:57 ` Rick Jones
2012-04-23 21:30 ` Eric Dumazet
2012-04-23 21:51 ` Rick Jones
2012-04-23 21:56 ` Rick Jones
2012-04-23 22:05 ` Eric Dumazet
2012-04-23 22:16 ` Rick Jones
2012-04-24 15:25 ` Christoph Lameter
2012-04-23 21:01 ` David Miller
2012-04-23 21:38 ` Eric Dumazet
2012-04-24 2:20 ` Eric Dumazet
2012-04-24 2:27 ` David Miller
2012-04-24 8:01 ` Ilpo Järvinen
2012-04-24 8:10 ` David Miller
2012-04-24 8:21 ` Ilpo Järvinen
2012-04-24 8:25 ` David Miller
2012-04-24 8:40 ` Ilpo Järvinen
2012-04-24 8:48 ` David Miller
2012-04-24 10:32 ` Ilpo Järvinen
2012-04-24 8:56 ` Eric Dumazet
2012-04-26 8:10 ` [RFC] allow skb->head to point/alias to first skb frag Eric Dumazet
2012-04-26 8:36 ` David Miller
2012-04-26 9:10 ` Eric Dumazet
2012-04-26 9:18 ` David Miller
2012-04-26 9:22 ` Eric Dumazet
2012-04-26 10:09 ` Maciej Żenczykowski
2012-04-26 12:32 ` Eric Dumazet
2012-04-26 13:50 ` Eric Dumazet
2012-04-26 20:12 ` David Miller
2012-04-26 20:18 ` Eric Dumazet
2012-04-24 8:49 ` [PATCH 2/2 net-next] tcp: sk_add_backlog() is too agressive for TCP Eric Dumazet
2012-04-24 8:44 ` David Laight
2012-04-24 8:53 ` Eric Dumazet
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