[Openib-windows] SRP performance tuning.

[Fabian Tillier]

Hi Erez,

On 3/30/06, Erez Cohen <erezc at mellanox.co.il> wrote:
>
> Hi Fab,
>
> In the Linux implementation of SRP initiator one can change several
> parameters (during the module loading) to tune performance. The most common
> parameters are: max_xfer_sectors_per_io and max_cmds_per_lun.
>
> Do you know if the same can be done in the Windows implementation of SRP
> initiator? Can you please explain how?

The driver reports no limits to the OS, so the limits end up being
either imposed by the OS or imposed by the driver when the the maximum
number of commands outstanding are issued.

The driver will support a maximum number of commands outstanding of
the number supported by the target with a maximum of 1000.  In
practice, the OS limits the number of oustanding requests per LUN to
254 - see the "Storport Queue Management" section in the DDK for a
description of how queueing is implemented.

The number of Scatter/Gather entries per I/O is reported as whatever
can fit into the Initiator to Target information unit, with a minimum
of 17.  This could be changed going forward to some tunable parameter
for targets that support only indirect data buffer descriptors and
thus have a small Initiator to Target information unit size.

Let me know if you have any other questions,

- Fab