Re: [Xenomai-help] i386 2.4 backport performing (too?) well

[Philippe Gerum <rpm@xenomai.org>]

Klaas Gadeyne wrote:
> On Fri, 2 Dec 2005, Philippe Gerum wrote:
> 
>> Klaas Gadeyne wrote:
> 
> [...]
> 
>>> For comparison, on the same hardware platform: - the RTAI 
>>> lxrt-latency on rtai 3.0r5 (adeos oldgen r18c1
>>>   patch for 2.4.31 also) test reports 38 usec
>>> - the latency test of xenomai 2.01 running on a 2.6.14-ipipe-1.0-10
>>>   kernel resulted in a latency of 80 usec.
>>
>>
>> 80 us on 2.6 is clearly pathological if 2.4 gives 30 us. All tests 
>> using 2.6.14-1.0-10 on dual SMP 750Mhz and 2.8Ghz, Geode 266 Mhz, 
>> Celeron 1Ghz, Centrino 1.6 Mhz and Pentium 90Mhz show a slight 
>> advantage for 2.4 over 2.6 (1-3%), but still in the error margin, I 
>> think. Maybe some option is enabled in your 2.6 configuration that 
>> might trigger this very high value?
> 
> 
> I rechecked the 2.6 config.  Apart from the lapic option, which I
> couldn't enable with xenomai [*], I can't see something obvious that I
> would have missed.  I'm sending you the config file in private.
> 
> Note that I haven't tested the 2.6 kernel with xenomai-trunk yet though...
> 
> thx,
> 
> Klaas
> 
> [*] When enabling local apic in the kernel configuration and booting
> with the lapic option, I get
> 

> Disable APIC support or pass "lapic" as boot param.
> 

lapic=1 on your boot line. This is not a Xeno issue, but a Linux kernel 
requirement. Using the local APIC is even recommended when available on 
your hw with Xeno.

> while loading xeno_hal.
> 
> 
> 


-- 

Philippe.