Date: Thu, 29 Apr 2010 23:07:15 -0600 From: Scott Long <scottl@samsco.org> To: Alexander Motin <mav@FreeBSD.org> Cc: freebsd-scsi@FreeBSD.org, FreeBSD Stable <freebsd-stable@FreeBSD.org>, Pete French <petefrench@ticketswitch.com>, Robert Noland <rnoland@FreeBSD.org> Subject: Re: MFC of "Large set of CAM improvements" breaks I/O to Adaptec 29160 SCSI controller Message-ID: <221F6444-3102-4CD7-A1A7-1DF4352E7F50@samsco.org> In-Reply-To: <4BDA6310.10902@FreeBSD.org> References: <E1O7PS0-00093c-9M@dilbert.ticketswitch.com> <BCD96E46-A669-457D-A3A4-4F2E6F84E6A8@samsco.org> <4BD98DE2.8020703@FreeBSD.org> <4A883035-3570-4FCC-B8EB-F205BD6D640D@samsco.org> <4BDA6310.10902@FreeBSD.org>
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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: >>>=20 >>> 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. >>>>>=20 >>>> For the record, queue-full is a common, expected condition in CAM. = It's not something that should be avoided =3D-) >>> Should we maybe have a counter in sysctl rather than flooding the = console with these messages then? >>=20 >> That's a pretty good idea. I'll make it happen. >=20 > 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. >=20 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. Scott
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