[LAU] 2.6.39.1 threadirqs vs. the rest: some numbers

[torbenh]

On Mon, Jun 13, 2011 at 05:38:11PM -0700, Fernando Lopez-Lezcano wrote:
> Hi all,
> 
> I just built a threaded-irqs enabled 2.6.39.1 kernel and used
> cyclictest to try to get an initial feeling of how good it might be.
> Cyclictest tests scheduling delays of the kernel it is running
> on[*]. These tests were run on a Fedora 13 T510 Lenovo laptop, with
> the ugly binary Nvidia driver (caveat emptor).
> 
> In the menu:
> 
>   2.6.39.1 with threaded irqs and PREEMPT active
>   2.6.33.13-rt31
>   2.6.34.8-rt31 (a forward port of rt31 to 2.6.34)
>   plain Fedora kernel (2.6.34.8-68.fc13.i686.PAE)
> 
> Now, before someone points it out, this is just a synthetic test
> that measures scheduling latency, not a real audio application.

still... it provides some numbers.
and what i get seems to differ from what you get pretty heavily.

---( torbenh at siel  )---( ~/cvs/rt-tests )---
-> uname -a
Linux siel 2.6.39 #53 SMP PREEMPT Wed May 25 22:11:00 CEST 2011 x86_64
GNU/Linux
---( torbenh at siel  )---( ~/cvs/rt-tests )---
-> ./cyclictest -t1 -p 80 -n -i 10000 -l 10000 -m
policy: fifo: loadavg: 2.34 1.27 0.54 5/267 10411          

T: 0 ( 7904) P:80 I:10000 C:  10000 Min:      8 Act:   19 Avg:   17 Max:
97
---( torbenh at siel  )---( ~/cvs/rt-tests )---


its just a single run. with a kernel compile in the background.
and thats WITHOUT threadirqs

> See below for details... (look at the "Avg:" and "Max:" latency
> values, those are in microseconds)
> 
> Unless I have done something wrong, it looks like we have a long way
> to go with regards to scheduling latency in anything other than
> 2.6.33 + rt patches. But, with threaded irqs in 2.6.39 maybe the
> performance with audio applications running under jack will be good
> anyway as we will be able to tune irq processing. Seems to me
> unlikely. I have not tested that yet.

you did not use -m ... although that didnt really change much for me.
but i have plenty of RAM here.

> 
> Tests were done after a clean reboot, initially with the machine
> idle and then while loading thunderbird with tons of emails and
> firefox with tons of pages. No audio work.

hmm... maybe i should have loaded up ff...
but i loaded midori. because ff was already running.

> 
> YMMV...
> -- Fernando
> 
> [*] https://rt.wiki.kernel.org/index.php/RT_PREEMPT_HOWTO
> 
> 
> ----------------------------------------------------------------------
> LENOVO T510
> 

-- 
torben Hohn