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

[Chris Worley]

On Mon, Sep 21, 2009 at 10:59 AM, Vladislav Bolkhovitin <vst at vlnb.net> wrote:
> Chris Worley, on 09/19/2009 01:31 AM wrote:
>>
>> On Mon, Sep 7, 2009 at 5:58 AM, Vladislav Bolkhovitin <vst at vlnb.net>
>> wrote:
>>>
>>> Chris Worley, on 09/06/2009 05:41 PM wrote:
>>>>
>>>> On Sun, Sep 6, 2009 at 3:36 PM, Chris Worley<worleys at gmail.com> wrote:
>>>>>
>>>>> On Sun, Sep 6, 2009 at 3:17 PM, Bart Van
>>>>> Assche<bart.vanassche at gmail.com>
>>>>> wrote:
>>>>>>
>>>>>> On Fri, Sep 4, 2009 at 1:20 AM, Chris Worley <worleys at gmail.com>
>>>>>> wrote:
>>>>>>>
>>>>>>> On Thu, Sep 3, 2009 at 11:38 AM, Chris Worley<worleys at gmail.com>
>>>>>>> wrote:
>>>>>>>>
>>>>>>>> I've used a couple of initiators (different systems) w/ different
>>>>>>>> OSes, w/ different IB cards (all QDR) and different IB stacks
>>>>>>>> (built-in vs. OFED) and can repeat the problem in all but the
>>>>>>>> RHEL5.2/OFED 1.4.1 target and initiator (but, if the initiator is
>>>>>>>> WinOF and the target is RHEL5.2/OFED1.4.1, then the problem does
>>>>>>>> repeat).
>>>>>>>
>>>>>>> Here's a twist: I used the Ubuntu initiator w/ one of the RHEL
>>>>>>> targets, and the RHEL initiator (same machine as was running WinOF
>>>>>>> from the beginning of this thread) w/ one of the Ubuntu targets: in
>>>>>>> both cases, the problem does not repeat.
>>>>>>>
>>>>>>> That makes it sound like OFED is the cure on either side of the
>>>>>>> connection, but does not explain the issue w/ WinOF (which does fail
>>>>>>> w/ either Ununtu or RHEL targets).
>>>>>>
>>>>>> These results are strange. Regarding the Linux-only tests, I was
>>>>>> assuming failure of a single component (Ubuntu SRP initiator, OFED SRP
>>>>>> initiator, Ubuntu IB driver, OFED IB driver or SRP target), but for
>>>>>> each of these components there is at least one test that passes and at
>>>>>> least one test that fails. So either my assumption is wrong or one of
>>>>>> the above test results is not repeatable. Do you have the time to
>>>>>> repeat the Linux-only tests ?
>>>>>
>>>>> Last night I was rerunning the RHEL5.2 initiator w/ Ubuntu client, and
>>>>> the problem repeated; now, I can't repeat the case where it didn't
>>>>> fail.  Still, no errors, other than the eventual timeouts previously
>>>>> shown; the target thinks all is fine, the initiator is stuck.
>>>>
>>>> ... and I haven't had any success w/ Ubuntu target and initiator, 8.10
>>>> or
>>>> 9.04.
>>>
>>> 1. Try with kernel parameter maxcpus=1. It will somehow relax possible
>>> races
>>> you have, although not completely.
>>
>> I finally got around to this test... 1 CPU works very well, w/o hangs
>> (will test all night to see if this holds true), 2 or more don't.
>> This is dual-socket NHM, so I can't specify more than one processor
>> w/o getting more than one socket.
>
> Where 1 CPU works well, on the target or initiator?

That was on the target.

> The race is on the
> corresponding host.
>
> I'd suggest you to reproduce the problem with the latest SCST trunk, lockdep
> enabled on the suspected host (better on both) and mgmt_minor trace level
> enabled on the target. Then, after the hang, let the system stay for about a
> half an hour, then send us with Bart (privately, compressed) kernel logs
> from both systems starting from the early boot messages.

I believe I comprehensively tested w/ Lockdep and complete scst
messages dumps on the target (and lockdep on the initiator) and came
up with no messages or lock issues salient to the issue.

If you think I should repeat this, I will.

>
> If you have dmesg only output, please enable printk timestamps
> (CONFIG_PRINTK_TIME).

Ubuntu has been pretty good about that.

Thanks,

Chris
>
>> Chris
>>>
>>> 2. Try with another hardware, including motherboard. You can have
>>> something
>>> like http://lkml.org/lkml/2007/7/31/558 (not exactly it, of course)
>>>
>>>> Chris
>>>>>
>>>>> Chris
>>>>>>
>>>>>> Bart.
>>>>>>
>
>