Am Freitag, 1. Juli 2005 00:27 schrieb Karsten Wiese:
> Am Donnerstag, 30. Juni 2005 22:50 schrieb Ingo Molnar:
> >
> > * Karsten Wiese <[email protected]> wrote:
> >
> > > Here come some numbers to back up the usefullness of
> > > CONFIG_X86_UP_IOAPIC_FAST. (and to show that my patch actually works
> > > ;-)) All measurement where taken on an UP Athlon64 2Ghz running 32bit
> > > 2.6.12-RT-50-35 PREEMPT_RT on a K8T800 mobo.
> >
> > thanks - the numbers are pretty convincing. I've applied most of your
> > patch (except the instrumentation bits), and it seems to work quite well
> > - one of my testsystems that had interrupt storms before can now run
> > IOAPIC_FAST. (i also enabled the option to be selectable for SMP kernels
> > too. If things work out fine we can make it default-on.) I've uploaded
> > the -50-39 patch with these changes included.
> >
> Ooops, you didn't apply this part of the patch:
>
> <snip>
> --- linux-2.6.12-RT-50-35/arch/i386/kernel/mpparse.c 2005-06-30 16:38:00.000000000 +0200
> +++ linux-2.6.12-RT/arch/i386/kernel/mpparse.c 2005-06-29 20:30:50.000000000 +0200
> @@ -263,6 +263,7 @@
> return;
> }
> mp_ioapics[nr_ioapics] = *m;
> + io_apic_base[nr_ioapics] = IO_APIC_BASE(nr_ioapics);
> nr_ioapics++;
> }
>
> @@ -914,6 +915,7 @@
> mp_ioapics[idx].mpc_apicaddr = address;
>
> set_fixmap_nocache(FIX_IO_APIC_BASE_0 + idx, address);
> + io_apic_base[idx] = IO_APIC_BASE(idx);
> mp_ioapics[idx].mpc_apicid = io_apic_get_unique_id(idx, id);
> mp_ioapics[idx].mpc_apicver = io_apic_get_version(idx);
> </snip>
>
> It provides the precalculation of the ioapics's virtual address.
> Or does IO_APIC_BASE() compile to an indexed lookup?
> then io_apic_base[] wouldn't be needed...
>
It is needed (only for optimization):
There are ioapics that have baseaddresses not on a page boundary.
Another idea: to merge the virtual ioapic base addresses into the io_apic_cache struct to use
the cpu-cache more efficiently ;-)
Karsten
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