[ofa-general] WinOF_2_0_5/SRP initiator: slow reads and eventually hangs

[Chris Worley]

I'm running a target comprised of: RHEL5.2/2.6.18-92.el5 (fresh off
the CD.. never updated) and it's embedded IB stack (not the latest
OFED) w/ SCST rev 1029 8-Aug-2009 ("svn info").

I'm running a W2008S (fully patched) initiator w/
MLNX_WinOF_2_0_5_wlh_x64_fre_2_0_5_4453.

Using Mellanox QDR cards/switch.

Writes over SRP, as measured from the initiator using IOMeter, get
proper performance (i.e. 1.2GB/s).

Reads get about 30% performance (i.e. 500MB/s instead of 1.6GB/s).
And while reading, IOMeter eventually hangs the system (Windows
becomes unresponsive to GUI interaction).  In this state, I see iostat
reporting transfers at the same low read rate from the target... so
there's IB traffic, but, given IOMeter's tasks are 10 minutes each, it
acts like it's a "skipping record" (sorry of you young folks don't
know what that is... but I can't think of another way to describe it)
and never moving on to the next benchmark, just endlessly repeating
the same I/O over and over again.  If I unload then reload the mlx4_ib
driver on the target, then the Windows system quickly returns, but
IOMeter remains hung and needs killed.

So, I have a lot of experimentation to do on the target in 1)
upgrading the target or changing the distro altogether and 2) using
OFED instead of built-in IB stack on the target to try to see if I can
budge this issue.

But, I was wondering if somebody might have a hint on this _or_ have a
known target distro/kernel setup that works reliably w/ Windows-based
SRP initiators.

Thanks,

Chris