Re: Linux 2.6.9 latencies: scheduler bug?

[Nick Piggin <nickpiggin@yahoo.com.au>]

Sami Farin wrote:
> On Mon, Oct 25, 2004 at 12:26:18AM +0300, Sami Farin wrote:
> ...
> 
>>while that's running, "rtc_latencytest 1024" has max latencies of 253ms.
>>$BLOCKLIST has around two thousand lines.
>>http://safari.iki.fi/ip_tables_original_maxlat_253ms.png
>>from pressing sysrq+p while it was running, I guesstimated one evil spot
>>and added cond_resched() in there :)
>>http://safari.iki.fi/ip_tables_cond_resched.png
>>at 5s I started the script.
> 
> 
> forget this stupid ip_tables.c patch, latencies have nothing to do with
> netfilter code, but bad interaction between xmms, rtc_latencytest
> and iptables.  I now get at max 3.1s (yup, 3100000us) latencies.
> http://safari.iki.fi/2.6.9-xmms-fun-1.png
> if you want to reproduce this:
> 1) run "rtc_latencytest 1024" (can't reproduce with "rtc_latencytest 512")
> 2) press play in xmms
> 3) start iptables-script
> 
> xmms has to be prepared first.
> a) put it in repeat mode
> b) start playing >= 2 files (like that short testcase.mp3 from lame)
> c) remove the files while xmms is playing
> d) wait till xmms has played all of the selected files
> e) press stop [now then you press play in 2), xmms does silly infinite
>    loop without delays while trying to open the songs]
> 
> please give me patches to try, 3.1s is really evil 8-)
> 

Don't think I've tried rtc_latency test. A quick search didn't turn
up its source code...

So... stupid question, is rtc_latencytest running with a realtime
scheduling policy?