RE: [RFC 0/2] mpt3sas/megaraid_sas : irq poll and load balancing of reply queue

[Kashyap Desai <kashyap.desai@broadcom.com>]

>
> In Summary,
> CPU completing IO which is not contributing to IO submission, may cause
cpu
> lockup.
> If CPUs count to MSI-X vector count ratio is X:1 (where X > 1) then
using irq poll
> interface, we can avoid the CPU lockups and by equally distributing the
> interrupts among the enabled MSI-x interrupts we can avoid performance
> issues.
>
> We are planning to use both the fixes only if cpu count is more than FW
> supported MSI-x vector.
> Please review and provide your feedback. I have appended both the
patches.

Hi -
Assuming method explained here is in-line with Linux SCSI subsystem and
there is no better method to fix such issue.
I am planning to provide the same solution for internal testing and
maintainers of respective driver (mpt3sas and megaraid_sas) will post
final patch to the upstream based on results.
As of now PoC results looks promising with the above mentioned solution
and no cpu lock was discovered.

>
> Thanks, Kashyap
>
>