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Ralf Mardorf wrote:
| Hi Free
| Free Ekanayaka wrote:
|> Hi Ralf,
|> Thanks for this interesting report, I was not aware about this issue,
|> as so far I blindely trusted the kernel experts
Probably not a bad idea. I know that there were some problems with IRQ
balancing but I don't really follow these things too closely anymore.
|> It would be great to have some tool, which automatically ajdusts your
|> modules and IRQs to get the best performance out of the system, but it
|> is a non-trivial task.
There are a lot of things you can do, it is probably worth mining the
kernel mailing list. For the moment there is not a lot we should have
to do other than blacklist the occasional module.
Lots of background info can be found on the following sites. Some of it
is CPU specific but there is good info nonetheless.
http://www.lesswatts.org/tips/cpu.php -- there is a section that talks
http://osdev.berlios.de/pic.html -- describes the modern APIC
http://www.irqbalance.org -- daemon for IRQ balancing. I know that the
kernel option for IRQ balancing had some issues with performance for a
while (2.6.9 era). I have no idea where this is at now. This is
packaged for Debian and Ubuntu btw so it should only be an apt-get away.
| I had a phone call with a hardware freak and get some informations. Now
| I knows a little bit more and that there are IRQ managers for Windows.
| That won't help us, but I guess there are some also for Linux. This
| managers won't do any thing full automatically.
|> For the moment I'd propose to start a page on the 64 Studio site in
|> order to collect information about tweaking IRQs and kernel modules.
| Thank you
|> RM> Is it true that handling interrupts manually might be impossible
|> RM> for laptops?
|> I'm not sure, but yes I guess so, some tweaks might be harder on
| The friend I had a phone call with told me that sometimes on any
| computer (using Windows) Interrupts won't be used, while others are
| overloaded and sometimes hardware gets no interrupt, while IRQs are
| free. He tried BIOS settings, desoldered a on-board modem, but (for
| Windows) sometimes he has no chance to get IRQs managed the way he tries
| to force them, in spite of BIOS functions, managing tools and hardware
There is a capable irqbalance program packaged for Debian et al. There
is also a kernel module of the same name that accomplishes a similar task.
Part of this depends on the APIC and the motherboard bios. There are a
number of things we can mess with using /proc or sysctl, look at the
source code and the lkml for more info. Generally we should not be
messing around in here (well we can but don't expect any improvements
with random changes).
| Looking at the varying /proc/interrupts of the 64 Studio that's broken
| for the sound cards since I tried to install the ATI driver, it might
| has to do with IRQs. Okay, I'm still a noob and I could be very, very
| wrong, but it's something I'll read more about.
| A page on the 64 Studio site would be a help. If there wasn't someone
| asking for IRQs in the list, I never would have thought about that some
| troubles I have, might has to do with IRQs.
It will be interesting to see if anything comes of this discussion.
Personally I believe it is much ado about nothing, but it would not be
the first time that I get surprised.
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