[8115] in linux-scsi channel archive
RE: scsi queue depth problem
daemon@ATHENA.MIT.EDU (Ralston, Steve)
Tue Feb 15 19:33:42 2000
Message-ID: <B2B3C90E45AED111B7B40001FA7E520A03833F5E@exw-kansas.ks.lsil.com>
From: "Ralston, Steve" <steve.ralston@lsil.com>
To: "'Douglas Gilbert'" <dgilbert@724.com>
Cc: "'eric@andante.org'" <eric@andante.org>,
linux-scsi@vger.rutgers.edu
Date: Tue, 15 Feb 2000 18:17:50 -0600
MIME-Version: 1.0
Content-Type: text/plain
Yes, you gather correctly. :-)
I was just cruising along doing periodic kernel source tree
updates while working on the (SCSI) driver, and happened
to notice that beating on the disk, well "sounded different"
after updating from linux-2.3.42. When I tried to figure out why,
I noticed lack of [any] usual:
<6>mpiscsi: Queue depth now {2-64}.
debug printk's in my sysklog... Indicating to me that I'm
choked down to 1 deep.
> If the midlevel restricts your device queue to 1 then
> that is a problem with either
> - the mid-level
> - or your driver's callback function provided to
> calculate queue depth.
The driver source did not change (famous last words) when
I noticed the choke down. Sooo, I guess that means
a problem introduced in the scsi mid-level? @2.3.43?
That's my big concern and why I posted to the linux-scsi list;
it's not nice to be cruising along and have things like this
change this underneath, but hey, that's linux life. :-)
How are you measuring the tagged queueing? From underneath
(bus analyser), inside your driver or from above (e.g. dd)?
Yes. :-) I noticed this inside the driver. Don't have FC analyzer
on there, but also measured / confirmed this inside the HAB
firmware processor(s) using ARM Multi-ICE debugger...
BTW: I'm pretty (99%) sure there's no problem with my 2.3.43,
2.3.44, 2.3.45+ikd, nor 2.3.45 stock kernel source trees.
I even dropped back to stock 2.3.45 kernel to make sure
my feeble hacks patching in 2.3.40-ikd2 weren't the culprit.
Thanks,
-SteveR
> -----Original Message-----
> From: Douglas Gilbert [SMTP:dgilbert@724.com]
> Sent: Tuesday, February 15, 2000 2:16 PM
> To: 'Ralston, Steve'; Douglas Gilbert
> Cc: 'eric@andante.org'
> Subject: RE: scsi queue depth problem
>
> Steve,
> So it works on 2.3.42 and is restricted to a queue length
> of 1 on 2.3.45 I gather. Perhaps you could try again to
> do what I suggested on 2.3.45 . If the midlevel restricts
> your device queue to 1 then that is a problem with either
> - the mid-level
> - or your driver's callback function provided to
> calculate queue depth.
>
> How are you measuring the tagged queueing? From underneath
> (bus analyser), inside your driver or from above (e.g. dd)?
> In the unlikely event you are using dd then I have a useful
> utility called sgp_dd that uses posix worker threads (up to
> 16) to push multiple scsi commands down a mid-level queue.
> While this is happening it can be observed with
> "cd /proc/scsi/sg/debug; cat debug"
> (if you are using the correct version of sg :-) ).
> You'll find this utility at http://www.torque.net/sg
>
>
> Doug Gilbert
>
> > -----Original Message-----
> > From: Ralston, Steve [mailto:steve.ralston@lsil.com]
> > Sent: Tuesday, February 15, 2000 12:35 PM
> > To: 'Douglas Gilbert'
> > Cc: 'eric@andante.org'
> > Subject: RE: scsi queue depth problem
> >
> >
> > Sorry again. I'd already stepped back to linux-2.3.42 kernel
> > when I tried loading sg. I see the CONFIG_PROC_FS stuff
> > didn't show up till 2.3.43.
> >
> > Not sure where to look next...
> >
> > Thanks,
> > -SteveR
> >
> > > -----Original Message-----
> > > From: Douglas Gilbert [SMTP:dgilbert@724.com]
> > > Sent: Tuesday, February 15, 2000 11:20 AM
> > > To: 'steve.ralston@lsil.com'
> > > Cc: 'eric@andante.org'
> > > Subject: RE: scsi queue depth problem
> > >
> > > Steve,
> > > You wrote (on the linux-scsi newsgroup):
> > > > > Perhaps you could load the sg driver and try:
> > > > > $ cd /proc/scsi/sg
> > > > > $ cat device_hdr devices
> > > > > $ cat host_hdr hosts
> > > > Sorry, I've tried loading the sg driver, but it is not
> > yielding ANY
> > > > /proc/scsi entries, even though I definitely have CONFIG_PROC_FS
> > > > set in my kernel/module builds. (I don't even see CONFIG_PROC_FS
> > > > anywhere in drivers/scsi/sg.c)
> > >
> > > It seems as though your kernel source tree has problems.
> > > According to a kernel source browser such as:
> > > http://zaphod.redwave.net/linux/kernel-2.3/
> > >
> > > CONFIG_PROC_FS appears 7 times in drivers/scsi/sg.c in
> > > 2.3.45 . Perhaps you should download the complete
> > > linux-2.3.45 source and retest your queuing problem.
> > >
> > > Doug Gilbert
> >
-
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