Alex,
When you get a chance I would ***love*** to take a look at your .config's if
you would not mind either posting them or emailing them directly. I have a
machine that I have not been able to quiet the latencies down sufficiently to
trust. From this info I see where I might have gone wrong...
Thanks for the information!!!
EBo --
Alexey Starikovskiy <[email protected]> said:
> Stephen Wille Padnos пиÑеÑ:
> Alexey Starikovskiy wrote:
>
>
>> Mark,
>> You are solving problem "backwords". You should just enable ACPI on your
>> realtime box to make it shutdown properly.
>> ACPI by itself does not worsen real time capabilities of your machine,
>> it is power management that do.
>>
>>
>>
> It seems to on some machines. Though it may work well for you or me,
> enabling ACPI in the kernels we distribute does reduce the number of PCs
> that have acceptable latency. If there have
>
>
Actually, by not enabling ACPI, you leave your machine in APM (legacy
power management) mode,
which require BIOS/SMI for any task.
>> You should definitely have CPU idle framework and ACPI processor driver
>> disabled. ACPI, ACPI button are perfectly fine.
>>
>>
>>
> I don't recall if it's only on the SMP kernels, but I know that some
> parts of ACPI have been enabled with good results on some machines.
> Part of the power control system is required to bring up the other cores
> in dual- and quad-core CPUs.
>
You are speaking about ACPI MADT table, which lists all processors and
interrupt controllers (APICs) for multiprocessor configurations. Without
it Linux can't configure anything but boot CPU.
Still, ACPI processor driver is not required for SMP.
>
>> If you care about latencies, you should also disable C1E support in BIOS
>> (if you have such option).
>> Saying this, I am having ~2-3msec average latencies on Celeron box with
>> the above settings and worst case is 8msec.
>>
>>
>>
> Did you intend to say milliseconds (0.001 seconds) or microseconds
> (0.000001 seconds) here?
>
>
Right, microseconds (us) :)
> If your'e talking about milliseconds, that is just about the worst
> latency I've ever heard of :)
>
> Assuming it's microseconds, that's one of the best. What hardware
> (motherboard, chipset, disk controller, ethernet controller, video card)
> are you using on that system? Also, what did you do to enable ACPI on
> your machine, and which parts did you enable? Did you build your own
> kernel? (if so, can you make the .config available online?) Did you
> use boot-time kernel options?
>
I have only 3 machines running, all Intel Celeron 430 based.
Shuttle K45
ASUS P5M-VM SE
Gigabyte GA31M -- this one I would not recommend, it requires SMI
disabling trick.
Onboard graphics and parallel and ethernet ports. SATA 3.5" disks.
15us delay on modern CPUs comes from C1E enabled by default in BIOS.
In kernel config I enable ACPI, Local APIC on single CPU (may not work
for everybody), and ACPI buttons.
No special kernel parameters.
I can't easily post my .config, as machines are in production
environment and not nearby.
Regards,
Alex.
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