[Openib-windows] SRP tuning

[Fabian Tillier]

Hi Yossi,

On 12/5/06, Yossi Leybovich <sleybo at dev.mellanox.co.il> wrote:
>
> I set:
>
> SCSI_MAXIMUM_TRANSFER_SIZE = SP_UNINITIALIZED_VALUE.
> SrbExtensionSize = 3552
>
> I played with the NumberOfPhysicalBreaks:
> The StorPort driver set the of NumberOfPhysicalBreaksvalue to 17 ( I don't
> know why , Can I configure?)

17 is the worst case number of breaks to transfer 64KB of data in a
single I/O.  You should be fine increasing this (I think the code
already increases it based on the SRB extension size).

> But even if I return 16/17 as my supported NumberOfPhysicalBreaks it keep
> post IOs with 8 s/g list size (32K)
> [when I set it to 4 ,storPort send IOs with 4 s/g , So the value did effect
> when I reduce it]
>
> Any idea why ?

What are you using to generate the I/O traffic?   Are you sure it's
issuing larger than 32K I/O sizes?  I've used iometer before with good
results.

-Fab