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

[Chris Worley]

On Tue, Sep 15, 2009 at 10:39 AM, Vladislav Bolkhovitin <vst at vlnb.net> wrote:
> Chris Worley, on 09/15/2009 03:03 AM wrote:
>>
>> On Mon, Sep 14, 2009 at 12:51 PM, Vladislav Bolkhovitin <vst at vlnb.net>
>> wrote:
>>>
>>> Chris Worley, on 09/11/2009 11:50 PM wrote:
>>>>
>>>> I've definitely removed the switch/firmware from being the cause.
>>>>
>>>> I'm thinking the reason you can't repeat the test may be latency
>>>> related.  We get ~50usecs average latency (on small block sizes),
>>>> which can't be achieved using regular SSD's (and rotating drives are
>>>> nowhere close).  Maybe a ramdisk would help repeat the issue.
>>>
>>> I think you should try to reproduce the problem with ramdisk or nullio.
>>> By
>>> so you will eliminate possible influence of the SSD backend.
>>
>> W/ 12GB RAM in the target, I created a 7GB ramdisk:
>>
>> mount -t ramfs -o size=7g ramfs /mnt/
>> dd if=/dev/zero of=/mnt/foo bs=1024k count=7000
>> echo "open ramdisk /mnt/foo" > /proc/scsi_tgt/vdisk/vdisk
>> echo "add ramdisk 2" >/proc/scsi_tgt/groups/Default/devices
>>
>> Then, on the initiator, I tested it... and it hung during sequential
>> 8KB block reads:
>>
>> fio --rw=read --bs=8k --numjobs=64 --iodepth=64 --sync=0 --direct=1
>> --randrepeat=0 \
>>   --group_reporting --ioengine=libaio --filename=/dev/sde --name=test
>> --loops=10000 --runtime=600
>>
>> Note that I was running the SM on the target this time too.
>
> Should you try then with iSCSI with IPoIB? It will eliminate the SRP stack.

I don't see this issue w/ iSCSI over IPoIB... I also don't see the performance.

Chris
>
>> Thanks,
>>
>> Chris
>>>
>>> Vlad
>>>
>>
>>
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>
>