Re: Real-Time Preemption, -RT-2.6.10-rc2-mm3-V0.7.31-13

[Gene Heskett]

On Monday 29 November 2004 10:23, Ingo Molnar wrote:
>* Ingo Molnar <mingo@xxxxxxx> wrote:
>> but please try to the -31-10 kernel that i've just uploaded, it
>> has a number of tracer enhancements:
>
>make that -31-13 (or later). Earlier kernels had a bug in where the
>process name tracking only worked for the first latency trace saved,
>subsequent traces showed 'unknown' for the process name. In -13 i've
>also added a printk that shows the latest user latency in a one-line
>printk - just like the built-in latency tracing modes do:
>
> (gettimeofday/3671/CPU#0): new 3068 us user-latency.
> (gettimeofday/3784/CPU#0): new 1008627 us user-latency.
>
>(this should also make it easier for helper scripts to save the
> traces, whenever they happen.)
>
> Ingo

I just built this to see how much blood it would draw, which isn't 
much.  I don't have jack here, so I don't have your standard torture 
test.  Instead, I run tvtime, which runs at a -19 priority.

I let it run about 30 seconds (untimed), noted that the frame error 
slippage wasn't improved, and got this output histogram when I quit 
it.

Its (tvtime) is running here of course.
--------------------
Nov 29 18:05:45 coyote kernel: Read missed before next interrupt
Nov 29 18:05:45 coyote kernel: wow!  That was a 22 millisec bump
Nov 29 18:05:45 coyote kernel: `IRQ 8'[846] is being piggy. 
need_resched=0, cpu=0
Nov 29 18:05:45 coyote kernel: Read missed before next interrupt
Nov 29 18:05:45 coyote kernel: wow!  That was a 22 millisec bump
Nov 29 18:05:45 coyote kernel: `IRQ 8'[846] is being piggy. 
need_resched=0, cpu=0
Nov 29 18:05:45 coyote kernel: Read missed before next interrupt
Nov 29 18:05:45 coyote kernel: wow!  That was a 21 millisec bump
Nov 29 18:05:45 coyote kernel: `IRQ 8'[846] is being piggy. 
need_resched=0, cpu=0
Nov 29 18:05:45 coyote kernel: Read missed before next interrupt
Nov 29 18:05:45 coyote kernel: wow!  That was a 21 millisec bump
Nov 29 18:05:45 coyote kernel: `IRQ 8'[846] is being piggy. 
need_resched=0, cpu=0
Nov 29 18:05:45 coyote kernel: Read missed before next interrupt
Nov 29 18:05:45 coyote kernel:

And was stopped here. 

Nov 29 18:05:45 coyote kernel: rtc latency histogram of {tvtime/3398, 
10609 samples}:
Nov 29 18:05:45 coyote kernel: 4 11
Nov 29 18:05:45 coyote kernel: 5 1716
Nov 29 18:05:45 coyote kernel: 6 4827
Nov 29 18:05:45 coyote kernel: 7 1495
Nov 29 18:05:45 coyote kernel: 8 382
Nov 29 18:05:45 coyote kernel: 9 193
Nov 29 18:05:45 coyote kernel: 10 206
Nov 29 18:05:45 coyote kernel: 11 188
Nov 29 18:05:45 coyote kernel: 12 148
Nov 29 18:05:45 coyote kernel: 13 202
Nov 29 18:05:45 coyote kernel: 14 195
Nov 29 18:05:45 coyote kernel: 15 95
Nov 29 18:05:45 coyote kernel: 16 70
Nov 29 18:05:45 coyote kernel: 17 23
Nov 29 18:05:45 coyote kernel: 18 18
Nov 29 18:05:45 coyote kernel: 19 8
Nov 29 18:05:45 coyote kernel: 20 9
Nov 29 18:05:45 coyote kernel: 21 1
Nov 29 18:05:45 coyote kernel: 22 1
Nov 29 18:05:45 coyote kernel: 26 1
--------------------
And I note that the 1-26 column of numbers does not seem to add up to 
whats being logged above there, which are all 21 and 22 ms bumps 
(whatever a bump is)

Is this a helpfull report, or just noise?  Subjectively, tvtime is 
running with far fewer visible frame glitches than before I started 
playing with these patches.  A marked improvement IMO.

-- 
Cheers, Gene
"There are four boxes to be used in defense of liberty:
 soap, ballot, jury, and ammo. Please use in that order."
-Ed Howdershelt (Author)
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by Gene Heskett are:
Copyright 2004 by Maurice Eugene Heskett, all rights reserved.
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