Re: [Xenomai-core] some results on my laptop

[Jim Cromie <jim.cromie@domain.hid>]

Philippe Gerum wrote:
>
>>
>> Ive been running an ipipe kernel as the default since shortly after 1/7.
>> Since then, Ive had a couple of freezes on boot,
>> and sometimes bash's auto-complete takes longer to complete,
>
> Eh? Maybe the CONFIG_PCI_MSI syndrom again?

Um, does this tell you anything ?

$ zcat /proc/config.gz | grep PCI_MSI
# CONFIG_PCI_MSI is not set

I noticed the slow completion when doing some heavy disk stuff,
lndir on a kernel tree, and probably diff -r on 2 kernel trees,
so the laptop was pretty busy.


>>
>> This was run on a pentium-M laptop,
>> with cpu-clock running at 600 MHz, (capable of 1.7 GHz)
>> I presume this might explain the negative latancies.
>> Im aware this is un-supported ..
>>
>
> The negative values are just there because even at 600Mhz, the timing 
> anticipation applied by the nucleus to compensate for the intrinsic 
> latency of the box is too high; i.e. the nucleus performs a bit too 
> well latency-wise, so the anticipated timer ticks end up being a bit 
> early on schedule. IOW, all is fine. Given the figures above, you 
> could probably reduce the anticipation factor by setting the 
> CONFIG_XENO_HW_SCHED_LATENCY (Machine menu) parameter to, say, 2500 
> nanoseconds (the default null value tells the nucleus to use the 
> pre-calibrated value, which might be higher than this for your setup).
>
Ok.  
with latencies == 0, calibration happens at runtime, so it would
reflect the current workload (and with cpufreq on) also would reflect
the current clock frequency, correct ?


> Btw, I'm not sure if you enabled the local APIC in your kernel config; 
> if you did not, you should: there is no reason to keep using the 
> braindamage 8254 PIT when a LAPIC is available with your CPU.
>
Ok, now running this.

zcat /proc/config.gz | grep APIC
CONFIG_X86_GOOD_APIC=y
CONFIG_X86_UP_APIC=y
CONFIG_X86_UP_IOAPIC=y
CONFIG_X86_LOCAL_APIC=y
CONFIG_X86_IO_APIC=y

[jimc@domain.hid latency]$ sudo ./run -- -T60 -s -t1
Password:
*
*
* Type ^C to stop this application.
*
*
== Sampling period: 100 us
== Test mode: in-kernel periodic task
warming up...
RTT|  00:00:05  (in-kernel periodic task, 100 us period)
RTH|-----lat min|-----lat avg|-----lat max|-overrun|----lat best|---lat 
worst
RTD|       -2165|      127216|     1399358|    7582|       -2165|     
1399358
RTD|       -2188|     -205817|     1403255|   16431|       -2188|     
1403255
RTD|       -2178|     -207605|     1399828|   25271|       -2188|     
1403255
RTD|       -2186|     -208602|     1402253|   34096|       -2188|     
1403255
RTD|       -2163|     -206835|     1399144|   42943|       -2188|     
1403255
RTD|       -2175|     -206848|     1401346|   51785|       -2188|     
1403255
RTD|       -2184|     -210270|     1396823|   60621|       -2188|     
1403255
RTD|       -2167|     -208781|     1399323|   69453|       -2188|     
1403255
RTD|       -2169|     -211121|     1397365|   78267|       -2188|     
1403255
RTD|       -2173|     -210119|     1398349|   87084|       -2188|     
1403255
RTD|       -2168|     -208425|     1400764|   95922|       -2188|     
1403255
RTD|       -2173|      211271|     1397470|  104678|       -2188|     
1403255
RTD|       -2170|     -208130|     1399794|  113508|       -2188|     
1403255
RTD|       -2161|     -208400|     1397968|  122334|       -2188|     
1403255
RTD|       -2162|     -211225|     1397581|  131139|       -2188|     
1403255
RTD|       -2175|     -210500|     1397274|  139951|       -2188|     
1403255
RTD|       -2179|     -207530|     1396890|  148781|       -2188|     
1403255
RTD|       -2178|     -207890|     1399275|  157611|       -2188|     
1403255
RTD|       -2172|     -207750|     1397386|  166432|       -2188|     
1403255
RTD|       -2175|     -206057|     1399763|  175260|       -2188|     
1403255
HSH|--param|--samples-|--average--|---stddev--
HSS|    min|        20|      2.000|      0.000
HSS|    avg|    205060|     90.399|     25.538
HSS|    max|        20|     99.000|      0.000
---|------------|------------|------------|--------|-------------------------
RTS|       -2188|     -170670|     1403255|  175260|    00:01:00/00:01:00


Obviously, the numbers dont look so good.
The test duration comments still apply.

> You should disable the ACPI support if enabled, and especially 
> everything related to the CPUfreq scaling and power suspend.
>
Given that Im not really developing any RT code,
and I like the laptop quiet and cool, Im inclined to keep
the CPUfreq scaling on, at least for my everyday kernel.
How much does CPUfreq invalidate results I might send (periodically)


thanks