NIC inerrupt

NIC inerrupt

[John Que]

Hello,

I want to count the number of times I reach an NIC receive
interrupt.

I added a global static variable of type int , and initialized
it to 0 ; each time I am in the rx_interrupt of the card I incerement
it by one;
I got large , non sensible numbers after one or two seconds;

So  for debug I added printk each time I increment it in rx_interrupt.

What I see is that there are  unreasonable jumps in the number

for instance , it inceremnts sequntially from 1 to 80,then jums to 4500, 
increments a little sequentially to 4580, and the jums again to
11000 ;

Is it got to do with it that this is in interrupt?
Any idea what it can be ?


(I also tried to declare it as static in the rx_interrupt method
and the same happened)

Thnx,
John

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Re: NIC inerrupt

[Denis Vlasenko]

On Monday 19 April 2004 15:46, John Que wrote:
> Hello,
>
> I want to count the number of times I reach an NIC receive
> interrupt.
>
> I added a global static variable of type int , and initialized
> it to 0 ; each time I am in the rx_interrupt of the card I incerement
> it by one;
> I got large , non sensible numbers after one or two seconds;
>
> So  for debug I added printk each time I increment it in rx_interrupt.
>
> What I see is that there are  unreasonable jumps in the number
>
> for instance , it inceremnts sequntially from 1 to 80,then jums to 4500,
> increments a little sequentially to 4580, and the jums again to
> 11000 ;
>
> Is it got to do with it that this is in interrupt?
> Any idea what it can be ?
>
>
> (I also tried to declare it as static in the rx_interrupt method
> and the same happened)

Show your code
-- 
vda

Re: NIC inerrupt

[Bart Samwel]

John Que wrote:
> Hello,
> 
> I want to count the number of times I reach an NIC receive
> interrupt.
> 
> I added a global static variable of type int , and initialized
> it to 0 ; each time I am in the rx_interrupt of the card I incerement
> it by one;
> I got large , non sensible numbers after one or two seconds;
> 
> So  for debug I added printk each time I increment it in rx_interrupt.
> 
> What I see is that there are  unreasonable jumps in the number
> 
> for instance , it inceremnts sequntially from 1 to 80,then jums to 4500, 
> increments a little sequentially to 4580, and the jums again to
> 11000 ;
> 
> Is it got to do with it that this is in interrupt?
> Any idea what it can be ?

You're probably reading the kernel output from syslog. Syslog 
periodically reads out the printks from the kernel. With the amount of 
printks you're doing you are probably printing info for about 4500 
interrupts between every time syslog checks for new kernel output, while 
the kernel buffer that is used to store this information can only handle 
   enough data for 80 interrupts.

--Bart

Re: NIC inerrupt

[John Que]

Hello,
thnxs;
You are right in that I send about 4500-5000 packets in a second.
I will try to print it every 1000  packets and see.
john


>From: Bart Samwel <bart@samwel.tk>
>To: John Que <qwejohn@hotmail.com>
>CC: linux-kernel@vger.kernel.org
>Subject: Re: NIC inerrupt
>Date: Mon, 19 Apr 2004 16:40:08 +0200
>
>
>
>John Que wrote:
>>Hello,
>>
>>I want to count the number of times I reach an NIC receive
>>interrupt.
>>
>>I added a global static variable of type int , and initialized
>>it to 0 ; each time I am in the rx_interrupt of the card I incerement
>>it by one;
>>I got large , non sensible numbers after one or two seconds;
>>
>>So  for debug I added printk each time I increment it in rx_interrupt.
>>
>>What I see is that there are  unreasonable jumps in the number
>>
>>for instance , it inceremnts sequntially from 1 to 80,then jums to 4500, 
>>increments a little sequentially to 4580, and the jums again to
>>11000 ;
>>
>>Is it got to do with it that this is in interrupt?
>>Any idea what it can be ?
>
>You're probably reading the kernel output from syslog. Syslog periodically 
>reads out the printks from the kernel. With the amount of printks you're 
>doing you are probably printing info for about 4500 interrupts between 
>every time syslog checks for new kernel output, while the kernel buffer 
>that is used to store this information can only handle   enough data for 80 
>interrupts.
>
>--Bart

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Re: NIC inerrupt

[Axel Weiß]

Am Montag, 19. April 2004 14:46 schrieb John Que:
> Hello,
>
> I want to count the number of times I reach an NIC receive
> interrupt.
>
> I added a global static variable of type int , and initialized
> it to 0 ; each time I am in the rx_interrupt of the card I incerement
> it by one;
> I got large , non sensible numbers after one or two seconds;
>
> So  for debug I added printk each time I increment it in rx_interrupt.
>
> What I see is that there are  unreasonable jumps in the number
>
> for instance , it inceremnts sequntially from 1 to 80,then jums to 4500,
> increments a little sequentially to 4580, and the jums again to
> 11000 ;
>
> Is it got to do with it that this is in interrupt?
> Any idea what it can be ?
>
>
> (I also tried to declare it as static in the rx_interrupt method
> and the same happened)

Probably you didn't declare your count variable 'volatile'?

Axel

-- 
Humboldt-Universität zu Berlin
Institut für Informatik
Signalverarbeitung und Mustererkennung
Dipl.-Inf. Axel Weiß
Rudower Chaussee 25
12489 Berlin-Adlershof
+49-30-2093-3050

Re: NIC inerrupt

[Richard B. Johnson]

On Tue, 20 Apr 2004, Axel [iso-8859-15] Weiß wrote:

> Am Montag, 19. April 2004 14:46 schrieb John Que:
> > Hello,
> >
> > I want to count the number of times I reach an NIC receive
> > interrupt.
> >
> > I added a global static variable of type int , and initialized
> > it to 0 ; each time I am in the rx_interrupt of the card I incerement
> > it by one;
> > I got large , non sensible numbers after one or two seconds;
> >
> > So  for debug I added printk each time I increment it in rx_interrupt.
> >
> > What I see is that there are  unreasonable jumps in the number
> >
> > for instance , it inceremnts sequntially from 1 to 80,then jums to 4500,
> > increments a little sequentially to 4580, and the jums again to
> > 11000 ;
> >
> > Is it got to do with it that this is in interrupt?
> > Any idea what it can be ?
> >
> >
> > (I also tried to declare it as static in the rx_interrupt method
> > and the same happened)
>
> Probably you didn't declare your count variable 'volatile'?
>
> Axel
>
> --
> Humboldt-Universität zu Berlin
> Institut für Informatik
> Signalverarbeitung und Mustererkennung
> Dipl.-Inf. Axel Weiß
> Rudower Chaussee 25
> 12489 Berlin-Adlershof
> +49-30-2093-3050

How about `cat /proc/interrupts`. That should tell him how
many interrupts the NIC got..

           CPU0
  0:     123073    IO-APIC-edge  timer
  1:       1131    IO-APIC-edge  keyboard
  2:          0          XT-PIC  cascade
 17:      18550   IO-APIC-level  BusLogic BT-958
 18:      69272   IO-APIC-level  eth0	<----------
NMI:          0
LOC:     123029
ERR:          0
MIS:          0

Do the simple stuff first. Only get compilcated if necessary.


Cheers,
Dick Johnson
Penguin : Linux version 2.4.26 on an i686 machine (5596.77 BogoMips).
            Note 96.31% of all statistics are fiction.