From: "Pasi Kärkkäinen" <pasik@iki•fi>
To: Alkis Georgopoulos <alkisg@gmail•com>
Cc: netdev@vger•kernel.org
Subject: Re: Bypass flow control problems
Date: Mon, 27 Dec 2010 15:43:46 +0200 [thread overview]
Message-ID: <20101227134346.GD2754@reaktio.net> (raw)
In-Reply-To: <1293040291.1777.36.camel@alkis>
On Wed, Dec 22, 2010 at 07:51:31PM +0200, Alkis Georgopoulos wrote:
> Hi,
>
> I'm an IT teacher/LTSP developer. In LTSP, thin clients are netbooted
> from a server and receive a lot of X and remote disk traffic from it.
>
> Many installations have a gigabit NIC on the server, an unmanaged
> gigabit switch, and 100 Mbps NICs on the clients.
>
> With flow control on, the server is limited to sending 100 Mbps to all
> the clients. So with 10 thin clients the server can concurrently send
> only 10 Mbps to each one of them.
>
> On NICs that support it, we turn flow control off and the server can
> properly send 100 Mbps to each client, i.e. 1 Gbps to 10 clients.
>
> * Is there any way to bypass that problem on NICs that do not support
> turning off flow control, like e.g. realteks?
> I.e. when a client sends a pause signal to the server, instead of the
> server pausing, to continue sending data to another client?
> Or even to limit the amound of data the server sends to each client,
> so that the clients never have to send pause signals?
>
You could set up QoS rules on the server to limit the network speed per client..
> * I really don't understand why flow control is enabled by default on
> NICs and switches. In which case does it help? As far as I
> understand, all it does is ruin gigabit => 100 Mbps connections...
>
> * As a side note, since rtl8169 is a very common chipset, is there a
> way to disable flow control for that specific NIC?
>
> This problem affects thousands of LTSP installations, we'd much
> appreciate your knowledge and feedback on it.
>
Did you try disabling flow control from the switch?
-- Pasi
next prev parent reply other threads:[~2010-12-27 14:19 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-12-22 17:51 Bypass flow control problems Alkis Georgopoulos
2010-12-27 13:43 ` Pasi Kärkkäinen [this message]
2010-12-29 5:05 ` Kirsher, Jeffrey T
2010-12-29 8:47 ` Pasi Kärkkäinen
2010-12-29 8:47 ` Alkis Georgopoulos
2010-12-29 8:49 ` Pasi Kärkkäinen
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