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

[Chris Worley]

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.

Thanks,

Chris
>
> Vlad
>