[9fans] Problem with outputing from kernel

[9fans] Problem with outputing from kernel

[dusan3sic]

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I added some logs in /sys/src/9/port/proc.c for some tests of the scheduler, I want to see at what moments do real time processes take the cpu. I did that with simple prints with the intention of doing cat /dev/kmesg > someFile because all the prints are stored there.  

The problem is that the flow of output just randomly stops at times and continues(only once by test) and i lose some of the output  which is really important. Any ideas why?

Also I was doing with tail -f /dev/kmesg in the background and without that /dev/kmesg loses the start of output up to some random moment where it shows it. Could the problem be that i have too many outputs?
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Re: [9fans] Problem with outputing from kernel

[ori]

Quoth dusan3sic@gmail.com:
> I added some logs in /sys/src/9/port/proc.c for some tests of the scheduler, I want to see at what moments do real time processes take the cpu. I did that with simple prints with the intention of doing cat /dev/kmesg > someFile because all the prints are stored there.  
> 
> The problem is that the flow of output just randomly stops at times and continues(only once by test) and i lose some of the output  which is really important. Any ideas why?

are you printing from an interrupt context? use iprint for that.

also, are you looking for trace(1)? we ship with a tool for showing
scheduler decisions.

> 
> Also I was doing with tail -f /dev/kmesg in the background and without that /dev/kmesg loses the start of output up to some random moment where it shows it. Could the problem be that i have too many outputs?

that's what tail *does*. It shows the tail (by default, last 10 lines) of the file.


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Re: [9fans] Problem with outputing from kernel

[Kurt H Maier via 9fans]

On Wed, Oct 04, 2023 at 07:18:23AM -0400, dusan3sic@gmail.com wrote:
> Also I was doing with tail -f /dev/kmesg in the background and without that /dev/kmesg loses the start of output up to some random moment where it shows it. Could the problem be that i have too many outputs?

try tail +0f /dev/kmesg

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Re: [9fans] Problem with outputing from kernel

[dusan3sic]

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https://9p.io/wiki/plan9/avoiding_screen_pollution_from_kernel_messages/index.html
this helped
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