From mboxrd@z Thu Jan 1 00:00:00 1970 From: Alexander Stein Subject: Re: [RESEND] [PATCH] net: CAN: at91_can.c: decrease likelyhood of RX overruns Date: Mon, 06 Oct 2014 16:14:05 +0200 Message-ID: <3545685.3jS4Whu5tJ@ws-stein> References: <1403775686-19352-1-git-send-email-david@protonic.nl> <2417882.RxeThGvgsF@ws-stein> <20141006133942.0f1c820b@archvile> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7Bit Return-path: Received: from webbox1416.server-home.net ([77.236.96.61]:48266 "EHLO webbox1416.server-home.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752750AbaJFONT (ORCPT ); Mon, 6 Oct 2014 10:13:19 -0400 In-Reply-To: <20141006133942.0f1c820b@archvile> Sender: linux-can-owner@vger.kernel.org List-ID: To: David Jander Cc: Marc Kleine-Budde , linux-can@vger.kernel.org, Wolfgang Grandegger , Oliver Hartkopp , "Hans J. Koch" On Monday 06 October 2014 13:39:42, David Jander wrote: > > > One interesting control-metric would be to monitor the amount of > > > messages/second your test-devices are able to generate. > > > > I just noticed that this testing hardware has a DDR2 with only 16bit > > interface. I think this will also reduce performance considerably. The > > 16-bit DDR2 (even at its lowest clock of 200MHz) is not exactly slow... why do > you think that could be a bottleneck? It's a 133MHz clock, so 266MHz effective. I had done similar tests with i.MX28-EVK which also has only a 16-bit DDR interface. The rusults were horrible. Even without that ethernet bug... Now, doing the same tests (also CPU and Memory) again, it is worse than a AT91SAM9G20 with 32-bit SDR RAM, which also has 400 MHz. I expected both would be equally. If you're correct and the RAM is not the bottleneck it seems that the cache (16kByte each, 32kByte on AT91SAM9G20) would be it. > > embedded device send ~1000 CAN frames/s, each which is an average busload of > > 20%, but in burst time, it should be 100%. > > You mean the bursts of 250 messages you talked about earlier should produce a > bus load of 100%? I think it is important to get some certainty about what's > really going on on the bus, specially if we see things we cannot explain. You > don't have access to a PC with a CAN interface or an oscilloscope, do you? My PC has our USB-CAN-Modules attached (single or dual channel), so what do you want to see? a candump log? My access to oscilloscopes rather limited and not reliable. Best regards, Alexander -- Dipl.-Inf. Alexander Stein SYS TEC electronic GmbH Am Windrad 2 08468 Heinsdorfergrund Tel.: 03765 38600-1156 Fax: 03765 38600-4100 Email: alexander.stein@systec-electronic.com Website: www.systec-electronic.com Managing Director: Dipl.-Phys. Siegmar Schmidt Commercial registry: Amtsgericht Chemnitz, HRB 28082