svn commit: r345056 - head/sys/dev/mrsas

[Rodney W. Grimes]

> Author: kadesai
> Date: Tue Mar 12 09:24:58 2019
> New Revision: 345056
> URL: https://svnweb.freebsd.org/changeset/base/345056
> 
> Log:
>   fw_outstanding"(outstanding IOs at firmware level) counter gets screwed up when R1 fastpath
>   writes are running. Some of the cases which are not handled properly in driver are:
>   
>   1. With R1 fastpath supported, single write from CAM layer can consume 2 MPT frames
>   at driver/firmware level for fastpath qualification(if fw_outstanding < controller Queue Depth).
>   Due to this driver has to throttle IOs coming from CAM layer as well as second fastpath
>   write(of R1 write) against Adapter Queue Depth.
>   If "fw_outstanding" reaches to adapter queue depth, driver should return IOs from CAM layer with
>   device busy status.While allocating second MPT frame(corresponding to R1 FP write) also, driver
>   should ensure fw_outstanding should not exceed adapter QD.
>   
>   2. For R1 fastpath writes completion, driver decrements "fw_oustanding" counter without
>   really returning MPT frame to free pool. It may cause IOs(with heavy IOs running, consuming whole
>   adapter Queue Depth) consuming MPT frames reserved for DCMDs(management commands) and
>   DCMDs(internal and sent by application) not getting MPT frame will start failing.
>   
>   Below is one test case to hit the issue described above-
>   1. Run heavy IOs (outstanding IOs should hit adapter Queue Depth).
>   2. Run management tool (Broadcom's storcli tool) querying adapter in loop (run command- "storcli64 /c0 show" in loop).
>   3. Management tool's requests would start failing due to non-availability of free MPT frames as all frames would be consumed by IOs.
>   
>   Fix: Increment/decrement of "fw_outstanding" counter should be in sync with MPT frame get/return.
>
>   Submitted by: Sumit Saxena <sumit.saxena at broadcom.com>
>   Reviewed by:  Kashyap Desai <Kashyap.Desai at broadcom.com>
>   Approved by:  Ken
>   MFC after:  3 days
>   Sponsored by:   Broadcom Inc
> 

Can we please keep commit messages formatted to <80 columns?

Thanks,
Rod

-- 
Rod Grimes                                                 rgrimes at freebsd.org