> Erez Zilber wrote:
> > Mike,
> >
> > I'm still investigating the performance problems in open-iscsi over iSER, 
> > and I think that I see the cause of the problem:
> >
> > I've added an outstanding commands counter. It's incremented when 
> > iscsi_queuecommand is called and decremented when iscsi_complete_command is 
> > called. After decrementing the counter, I save it's value in some global 
> > array. I print this array when iscsi_session_teardown is called.
> >
> >From what I see, in ~25% of command completions, the command queue is empty 
> >(i.e. outstanding_cmds = 0). This can explain the low throughput that I see 
> >with iSER.
> >
> > What could be the cause for that? Is there anything not well configured in 
> > the scsi_host_template that we use? Anything else?
> >
> I saw this when using all io schedulers except noop. When I set the
> queue to use noop, The iscsi queue was full (host_busy was greater than
> 1) most of the time and thoughout was higher. I was going by just checking
> /sys/class/scsi_host/hostX/host_busy


I'm not familiar with "io schdulers". What's that? You're not talking about 
benchmraks, right?

I wasn't aware of /sys/class/scsi_host/hostX/host_busy. I will take a look.

> which if I underatnd your patch right is similar to what you are doing.
> I will run your patch to double check though.
> Also I think you can tweak the other schedulers to fix the problem, but
> I have not found the right combo yet.

Again, if you can say a few more words about the schdulers. Where do I set it?




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