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    SubjectRe: Interrupts are being dropped under heavy IO on -rt .
    Andrew Vasquez wrote:
    > On Fri, 10 Apr 2009, jvrao wrote:
    >> Qlogic driver uses MSI-EDGE interrupts by default.
    >> On -rt kernel under heavy IO load we observed that the driver missed
    >> interrupts occasionally.
    >> Missing interrupts caused spurious mailbox timeouts and path failovers.
    >> Suspecting MSI interrupts, we disabled MSI and forcing the driver to use
    >> APIC interrupts (Patch attached).
    >> With this change, our IO tests ran for extended period of time without
    >> any issues.
    >> It would be interesting to see if the MSI infrastructure itself has
    >> issues on realtime, or it is the combination of qla2xxx/MSI.
    >> Right now we don't have any setup to test out MSI with other adapters.
    >> Hence, wondering if anyone faced similar issues.
    > Could you perhaps provide some details on hardware used within your
    > testing -- HBA type, storage, etc? Also, can you share any logs of
    > the failures with extended-error-logging enabled
    > (ql2xextended_error_logging)?

    Hi, the following link provides more information on the logs and our analysis.

    [root@elm3c29 R2-SR1]# lspci | grep -i qlogic
    03:05.0 Fibre Channel: QLogic Corp. ISP2422-based 4Gb Fibre Channel to PCI-X HBA (rev 02)
    03:05.1 Fibre Channel: QLogic Corp. ISP2422-based 4Gb Fibre Channel to PCI-X HBA (rev 02)

    Storage is DS4700 (Product ID: 1814)

    If you need more information, please let me know, I can generate more information/logs.
    I will also find time to reproduce this with ql2xextended_error_logging enabled.


    > Regards,
    > Andrew Vasquez
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