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    SubjectRe: What determines which interrupts are shared under Linux?
    Alan Cox wrote:
    > Ar Maw, 2006-08-15 am 09:17 -0500, ysgrifennodd Roger Heflin:
    >> On Linux when interrupts are defined similar to below, what defines say
    >> ide2, ide3 to be on the same interrupt? The bios, linux, the driver using
    >> the interrupt? And can that be controlled/overrode at the
    >> kernel/driver level?
    >
    > Only with a soldering iron. They are the way the system is wired. Moving
    > boards between slots may change the IRQ allocation.
    >
    >> I have identified that the disks that are shared on ide2, ide3 do funny
    >> things when both are being heavily used (dma_expiry), this is an older
    >> driver versions
    >
    > That could be occuring just through lack of PCI bus bandwidth.
    >
    >
    >

    Right now, all controllers are part of the NVIDIA chipset which should
    mean the are on the same PCI bandwidth. The block diagram does indicate
    the 4 sata channels as one unit, though I don't know exactly how things
    were internally done, performance testing seems to indicate that all
    3 I am using are independent hardware as they don't seem to affect each
    others load.

    I am currently retesting under 2.6.17.8 to see if I have similar issues
    there, under that it show interrupts like below, different interrupt
    numbers,
    but similar sharing as ata1/ata2, and ata3/ata4 are on the same interrupt.

    ata1: SATA max UDMA/133 cmd 0xEC00 ctl 0xE802 bmdma 0xDC00 irq 16
    ata2: SATA max UDMA/133 cmd 0xE400 ctl 0xE002 bmdma 0xDC08 irq 16
    ata1: SATA link up 3.0 Gbps (SStatus 123)
    ata1: dev 0 cfg 49:2f00 82:706b 83:7e61 84:4023 85:7069 86:3e41 87:4023
    88:407f
    ata1: dev 0 ATA-7, max UDMA/133, 321672960 sectors: LBA48
    ata1: dev 0 configured for UDMA/133
    ata2: SATA link up 3.0 Gbps (SStatus 123)
    ata2: dev 0 cfg 49:2f00 82:706b 83:7e61 84:4023 85:7069 86:3e41 87:4023
    88:407f
    ata2: dev 0 ATA-7, max UDMA/133, 321672960 sectors: LBA48
    ata2: dev 0 configured for UDMA/133
    ata3: SATA max UDMA/133 cmd 0xD800 ctl 0xD402 bmdma 0xC800 irq 17
    ata4: SATA max UDMA/133 cmd 0xD000 ctl 0xCC02 bmdma 0xC808 irq 17
    ata3: SATA link up 3.0 Gbps (SStatus 123)
    ata3: dev 0 cfg 49:2f00 82:706b 83:7e61 84:4023 85:7069 86:3e41 87:4023
    88:407f
    ata3: dev 0 ATA-7, max UDMA/133, 321672960 sectors: LBA48
    ata3: dev 0 configured for UDMA/133
    ata4: SATA link down (SStatus 0)

    Roger
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