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List:       freebsd-scsi
Subject:    Re: MFC of "Large set of CAM improvements" breaks I/O to Adaptec
From:       Alexander Motin <mav () freebsd ! org>
Date:       2010-04-30 5:16:11
Message-ID: 4BDA679B.1000706 () FreeBSD ! org
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Scott Long wrote:
> On Apr 29, 2010, at 10:56 PM, Alexander Motin wrote:
> > Scott Long wrote:
> > > On Apr 29, 2010, at 7:47 AM, Robert Noland wrote:
> > > > Scott Long wrote:
> > > > > On Apr 29, 2010, at 2:50 AM, Pete French wrote:
> > > > > > > Thanks. First step successful - I can steadily reproduce problem on
> > > > > > > CURRENT. raidtest with 200 I/O streams over gmirror of two disks on \
> > > > > > > same channel triggers issue in seconds. Any I/O on channel dying after \
> > > > > > > both disks report "Queue full" error same time. The rest of system \
> > > > > > > works fine. If I preliminarily manually adjust queue depth of one disk \
> > > > > > > - everything works fine. I'll investigate it tomorrow.
> > > > > > Glad you have managed to dupliate it - the queue depth thing is
> > > > > > inetersting, what changes did you make ? I can try them here and see
> > > > > > if they improve the situation on either of my two machines.
> > > > > > 
> > > > > For the record, queue-full is a common, expected condition in CAM.  It's \
> > > > > not something that should be avoided =-)
> > > > Should we maybe have a counter in sysctl rather than flooding the console \
> > > > with these messages then?
> > > That's a pretty good idea.  I'll make it happen.
> > It is already hidden behind bootverbose. Hiding it deeper will make
> > unclear why CAM requeues the rest of commands (also reported under
> > bootverbose). I've tuned log messages a bit recently and they seem to be
> > more consistent and readable now IMHO.
> 
> We used to run FreeBSD at Yahoo with bootverbose turned on in order to help with \
> debugging.  After years of doing this, I finally turned bootverbose off last year, \
> partially because of the excessive console spam produced by these queue-full \
> messages.  Even when we were writing the ahc/ahd drivers at Adaptec years ago, I \
> never really liked these messages, and we rarely ran with bootverbose turned on \
> unless we were actively developing code or debugging a problem.  I like Robert's \
> suggestion because not only does it make running with bootverbose less painful, it \
> can also provide counters and also calculate and report rate measurements that \
> might be more useful than just the printf. 
> If you feel strongly against it, I won't push it, but I do like the suggestion.

No. I just wanted to say that requeue messages massively logged in that
case are even less informative for regular user.

-- 
Alexander Motin
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