netdev - Re: [PATCH v2 1/2] can: Decrease default size of CAN

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Date:	Thu, 23 Jan 2014 22:01:37 +0100
From:	Marc Kleine-Budde <mkl@...gutronix.de>
To:	David Miller <davem@...emloft.net>, sojkam1@....cvut.cz
CC:	linux-can@...r.kernel.org, netdev@...r.kernel.org
Subject: Re: [PATCH v2 1/2] can: Decrease default size of CAN_RAW socket send
 queue

On 01/23/2014 09:41 PM, David Miller wrote:
> From: Michal Sojka <sojkam1@....cvut.cz>
> Date: Wed, 22 Jan 2014 09:27:36 +0100
> 
>> Since the length of the qdisc queue was set by default to 10
>> packets, this is exactly what was happening.
> 
> This is your bug, set the qdisc limit to something more reasonable.
> 
> Something large enough to absorb the traffic wrt. the speed at which
> the CAN device can sink the data.

Hmmm, the problem is on i686 I have to increase the txqueuelen to 366
before the socket works as expected (writes are blocking). This means if
there are two processes one sending a stream of bulk data and the other
one occasionally more important data there will be a lot of frames in
front of the important ones.

With Michal's patch we can limit the number of frames in flight to a
reasonably low amount.

> These two patches are something I am not willing to apply to my
> tree, this is not how you solve this problem, sorry.

Marc

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