Messages in this thread | | | Date | Thu, 26 Jul 2007 12:45:17 +0200 | From | John Sigler <> | Subject | Re: Pin-pointing the root of unusual application latencies |
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John Sigler wrote:
> Len Brown wrote: > >> John Sigler wrote: >> >>> # cat /proc/interrupts >>> CPU0 >>> 0: 37 XT-PIC-XT timer >>> 1: 2 XT-PIC-XT i8042 >>> 2: 0 XT-PIC-XT cascade >>> 7: 0 XT-PIC-XT acpi >>> 10: 175 XT-PIC-XT eth2, Dta1xx >>> 11: 1129 XT-PIC-XT eth0 >>> 12: 4 XT-PIC-XT eth1 >>> 14: 21482 XT-PIC-XT ide0 >>> NMI: 0 >>> LOC: 161632 >>> ERR: 0 >>> MIS: 0 >>> >>> IRQ 10 is shared between a NIC and an I/O board. >>> >>> For eth2, the kernel said: >>> ACPI: PCI Interrupt 0000:00:0a.0[A] -> Link [LNKC] >>> -> GSI 10 (level, low) -> IRQ 10 >>> >>> For Dta1xx, the kernel said: >>> ACPI: PCI Interrupt 0000:02:0e.0[A] -> Link [LNKC] >>> -> GSI 10 (level, low) -> IRQ 10 >>> >>> Is it possible to avoid the two boards sharing IRQ 10? >> >> Maybe. In this configuration, INTA of the two devices >> is physically connected to the same wire on the device-side >> of the interrupt re-mapper -- so you'd have to change the configuration. >> If you have an IOAPIC and can enable it, that will not hurt -- > > I believe this board does not provide an IO-APIC. > Even the LAPIC is disabled in the BIOS. > (Why would they do that??) > >> though unless something else changes, these devices are still >> tied together on the device-side of the mapper. >> So if you can physically move one of the devices to another slot >> that is your best bet.
The NICs are on-board, therefore it is not possible to move them.
The motherboard only has one PCI slot, so the manufacturer includes a backplane (is that what it's called?) to provide two PCI slots.
The results I've given so far were with the I/O board inserted in the bottom slot. If it is inserted in the top slot, the results are different indeed.
# cat /proc/interrupts CPU0 0: 37 XT-PIC-XT timer 1: 2 XT-PIC-XT i8042 2: 0 XT-PIC-XT cascade 5: 20270 XT-PIC-XT Dta1xx 7: 0 XT-PIC-XT acpi 10: 4 XT-PIC-XT eth2 11: 2639 XT-PIC-XT eth0 12: 4 XT-PIC-XT eth1 14: 13984 XT-PIC-XT ide0 NMI: 0 LOC: 518501 ERR: 0 MIS: 0
$ diff dmesg.adlink dmesg2.adlink 208c208,210 < ACPI: PCI Interrupt 0000:02:0e.0[A] -> Link [LNKC] -> GSI 10 (level, low) -> IRQ 10 --- > ACPI: PCI Interrupt Link [LNKD] enabled at IRQ 5 > PCI: setting IRQ 5 as level-triggered > ACPI: PCI Interrupt 0000:02:0f.0[A] -> Link [LNKD] -> GSI 5 (level, low) -> IRQ 5
$ diff lspci.adlink lspci2.adlink 121c121 < 02:0e.0 Multimedia controller: PLX Technology, Inc. 9056 PCI I/O Accelerator --- > 02:0f.0 Multimedia controller: PLX Technology, Inc. 9056 PCI I/O Accelerator 126c126 < Interrupt: pin A routed to IRQ 10 --- > Interrupt: pin A routed to IRQ 5
I'll give a 4-port PCI NIC a spin.
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