From mboxrd@z Thu Jan 1 00:00:00 1970 From: Martin Kozusky Subject: Re: CAN messages being lost on i.MX25 with flexcan Date: Fri, 20 Apr 2012 07:51:00 +0200 Message-ID: References: <4F8FEF02.7040503@grandegger.com> <4F8FFAB3.1040906@grandegger.com> <4F901500.9070009@grandegger.com> Mime-Version: 1.0 Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Return-path: Received: from plane.gmane.org ([80.91.229.3]:43200 "EHLO plane.gmane.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751256Ab2DTFvN (ORCPT ); Fri, 20 Apr 2012 01:51:13 -0400 Received: from list by plane.gmane.org with local (Exim 4.69) (envelope-from ) id 1SL6kQ-00022n-AX for linux-can@vger.kernel.org; Fri, 20 Apr 2012 07:51:10 +0200 Received: from 213.191.105.242 ([213.191.105.242]) by main.gmane.org with esmtp (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 20 Apr 2012 07:51:10 +0200 Received: from mkozusky by 213.191.105.242 with local (Gmexim 0.1 (Debian)) id 1AlnuQ-0007hv-00 for ; Fri, 20 Apr 2012 07:51:10 +0200 In-Reply-To: <4F901500.9070009@grandegger.com> Sender: linux-can-owner@vger.kernel.org List-ID: To: linux-can@vger.kernel.org Dne 19.4.2012 15:37, Wolfgang Grandegger napsal(a): > On 04/19/2012 01:58 PM, Martin Kozusky wrote: >> Dne 19.4.2012 13:44, Wolfgang Grandegger napsal(a): >>> On 04/19/2012 01:21 PM, Martin Kozusky wrote: >>>> Dne 19.4.2012 12:54, Wolfgang Grandegger napsal(a): >>>>> On 04/19/2012 12:04 PM, Martin Kozusky wrote: >>>>>> Hello, >>>>>> I'm using Voipac i.MX25 module with flexcan, kernel 2.6.38.9. >>>>>> I'm sending the data at 250kbps, around 1100 msgs/sec. When I >>>>>> enable the >>>>>> canbus interface (canconfig can0 start), CPU load is higher, that is >>>>>> understandable, there are many interrupts. I'm not doing anything else >>>>>> then using recvmsg (or recvmmsg which is little better), but some >>>>>> messages are still lost (around 1500 messages lost from 467 000 being >>>>>> send from another source). When I start doing something (like "cat >>>>>> /proc/interrupts", or write to file), many more messages are lost. >>>>>> >>>>>> Do you have any idea how to fix this? I need to make some CAN messages >>>>>> logger and I cannot lose any message (idealy :) So I made big >>>>>> buffer in >>>>>> my program so that I don't need to write the messages into the file >>>>>> while "recording" is enabled, after "recording" is switched off, I >>>>>> write >>>>>> the buffer into the file, but that is still not good enough. >>>>>> Is there any way how to write to some buffer directly in flexcan >>>>>> driver >>>>>> (the best would be in the IRQ routine) and then read messages from >>>>>> this >>>>>> buffer in my program? >>>>>> Or are just interrupts lost when doing something else in the system >>>>>> and >>>>>> I cannot fix this? Or can I somehow specify that "can rx >>>>>> interrupts" has >>>>>> highest prioroty? >>>>> >>>>> Do you already know where the packets are dropped (get lost). Maybe >>>>> your >>>>> user space app is simply not faster enough to process them in time. You >>>>> can check that with the candump option "-d". >>>> >>>> Hello Wolfgang, >>>> I don't know where it gets lost. But I'm just making select() and >>>> recvmmsg in my app now. >>>> Now when I'm trying candump -d, it shows messages and between that: >>>> >>>> can0 18FFC33D [8] 4A E6 00 00 03 00 00 F6 >>>> can0 1CEFB8F3 [8] 34 42 23 3D 8C 01 00 00 >>>> DROPCOUNT: dropped 245 CAN frames on 'can0' socket (total drops 30886) >>>> can0 18FF0AEF [8] 70 76 46 7C A7 9E 2A 6A >>>> can0 18FF0AF0 [8] B0 7E FB 7D A7 DC 27 69 >>>> can0 18FEBF0B [8] F5 03 79 81 69 74 6E 79 >>>> >>>> I've sent around 40 000 messages. >>>> Does this help somehow to identify where the problem is? >>> >>> Yes, you are loosing messages because your app is not faster enough. >>> >>>> I found out that if I (in my program) don't printf every frame, then >>>> dropcount is better, so I think when candump would only show dropps and >>>> not every frame then it would also get better. >>> >>> printf takes time, of course. Therefore everything which makes your app >>> reading the messages faster will help including increasing the >>> scheduling priority of the process/thread. Also increasing the size of >>> the receive buffer may help. Try candump with the "-r" option. >> >> I tried -r 10000000 >> >> and the result was that dropping started some time later then it would >> normaly. From 467 000 packets, total drops was 103064. That is better >> ratio than before. But few times, my system was stucked for a while, >> then it recovered and continued to work. So I will try to use this >> buffer size in my program, without printf and I will see how many >> packets I lose. > > If other activities delay your app too much, your are in trouble. Proper > thread priorities may help. So I tried my app with bigger receive buffer and saving data into memory and it looks like no messages are lost now :) (but when I write them into file, they are lost, but I can use the temp memory storage, so I can live with that :) >> Is there a way how to get actual used size of the buffer? > > getsockopt? > >>>> This is my /proc/interrupts >>>> >>>> root@vmx25 /opt$ cat /proc/interrupts >>>> CPU0 >>>> 0: 0 - spi_imx >>>> 5: 32827 - IMX-uart >>>> 9: 129 - sdhci >>>> 13: 0 - spi_imx >>>> 25: 5 - imxdi_rtc >>>> 33: 12168 - mxc_nand >>>> 34: 1 - mxc-sdma >>>> 37: 109275 - ehci_hcd:usb1 >>>> 43: 1624971 - can0 >>>> 46: 0 - mxcadc >>>> 54: 195357 - i.MX Timer Tick >>>> 164: 0 - ESDHCI card 0 detect >>>> Err: 0 >>> >>> In a first place, I don't think your are loosing messages because they >>> are not read-out faster enough from the CAN controller. >>> >>>> I have another problem - when I send messages and nobody is acking them >>>> (no other device on CANbus), system stops responding until I put another >>>> device onto CANbus, but I think I should start new thread with this. >>> >>> What kernel version do you use? Do you use the flexcan driver from that >>> kernel? The problem is bus errors coming at high rate. >> >> I'm using 2.6.35.9 Preempt, the flexcan.c driver is original. > > IIRC, that kernel version did not include the flexcan driver. It entered > with 2.6.36. Anyway, maybe the following patch helps: > > http://patchwork.ozlabs.org/patch/130761/ It seems that it helped :) when nobody is ACKing, it doesn't hang. Thank you, Martin > Wolfgang. > -- > To unsubscribe from this list: send the line "unsubscribe linux-can" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >