Date: Fri, 13 Feb 2009 13:18:05 +0000 From: Tom Evans <tevans.uk@googlemail.com> To: Scott Long <scottl@samsco.org> Cc: FreeBSD Stable <freebsd-stable@freebsd.org> Subject: Re: HEADS UP: Major CAM performance regression Message-ID: <1234531085.2998.42.camel@localhost> In-Reply-To: <499551B9.7050805@samsco.org> References: <499551B9.7050805@samsco.org>
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On Fri, 2009-02-13 at 03:55 -0700, Scott Long wrote: > All, > > A major performance regression was introduced to the CAM subsystem in > FreeBSD 7.1. The following configurations are known to be affected: > > VMWare ESX > VMWare Fusion > (using bt or lsilogic controller options) > HP CISS RAID > Some MPT-SAS combinations with SATA drives attached > (Includes Dell SAS5/ir, but not PERC5/PERC6). > > Pure SCSI and SAS subsystems likely are NOT affected. Any hardware > that uses the 'ata' driver is also definitely NOT affected. To > determine if your installation is affected, run the following command as > root: > > camcontrol tags da0 > > Substitute 'da0' with another appropriate drive device number, if > needed. Note that this ONLY AFFECTS 'da' DEVICES. If your disks are > 'ad' devices, they are NOT affected. > > The result from running this command should be an output similar to the > following: > > (pass0:mpt0:0:8:0): device openings: 255 > > If, instead, it reports a value of '1', you are likely affected. Note > that it may be normal for USB memory devices to report a low number. > Also, many legacy SCSI disks, and devices that are not disks, may also > be expected to report a low number. > > The effect of this problem is that only one I/O command will be issued > to the controller and disk at a time, instead of overlapping multiple > commands in parallel. This causes significantly higher latency in > servicing moderate and heavy I/O workloads, leading to very poor > performance. Performance can be easily compared by downgrading to > FreeBSD 7.0. > > I have committed a fix for this problem for FreeBSD 8-CURRENT as of SVN > revision 188570. FreeBSD 7-STABLE will be updated with the fix in a few > days once I've gotten confirmation that the fix works and doesn't cause > any adverse side-effects. Anyone wanting to help in this validation > effort should apply the attached patch to their kernel source tree and > recompile. Please contact me directly by email to report if the problem > is fixed for you. > > If the validation process goes smoothly, I will work with the release > engineering team to turn this fix into an official errata update for > FreeBSD 7.1. > > Thanks in advance for your help. > > Scott > Hi Scott I have one da0 device, a USB attached hard disk: umass0: <LaCie LaCie Hard Drive USB, class 0/0, rev 2.00/0.00, addr 2> on uhub6 da0 at umass-sim0 bus 0 target 0 lun 0 da0: <SAMSUNG SP2514N VF10> Fixed Direct Access SCSI-2 device da0: 40.000MB/s transfers da0: 238475MB (488397168 512 byte sectors: 255H 63S/T 30401C) camcontrol shows: > $ sudo camcontrol tags da0 (pass0:umass-sim0:0:0:0): device openings: 1 Is that to be expected? This is RELENG_7 from October '08: FreeBSD strangepork.mintel.co.uk 7.1-PRERELEASE FreeBSD 7.1-PRERELEASE #0: Wed Oct 22 02:25:56 BST 2008 root@sweetpork.pc.mintel.co.uk:/usr/FreeBSD/RELENG_7/obj/usr/FreeBSD/RELENG_7/src/sys/STRANGEPORK i386 Thanks Tom
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