Date: Fri, 22 Apr 2005 09:56:50 -0600 From: Scott Long <scottl@samsco.org> To: Daniel Eriksson <daniel_k_eriksson@telia.com> Cc: 'FreeBSD Current' <freebsd-current@freebsd.org> Subject: Re: Serious I/O problems (bad performance and live-lock) Message-ID: <42691EC2.7080106@samsco.org> In-Reply-To: <!~!UENERkVCMDkAAQACAAAAAAAAAAAAAAAAABgAAAAAAAAA0VcX9IoJqUaXPS8MjT1PdsKAAAAQAAAAKDq8qQ2O9UK7PKMOCt2NqwEAAAAA@telia.com> References: <!~!UENERkVCMDkAAQACAAAAAAAAAAAAAAAAABgAAAAAAAAA0VcX9IoJqUaXPS8MjT1PdsKAAAAQAAAAKDq8qQ2O9UK7PKMOCt2NqwEAAAAA@telia.com>
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Daniel Eriksson wrote: > With recent CURRENT (at least for the last 2 days, but probably longer), two > of my systems can be brought to their knees (live-lock) with a simple "dd > if=/dev/zero of=test bs=128k" command. I have not tested any other systems. > > I keep both servers synced running 6-CURRENT: > > Server #1: dual AthlonMP 2600+, Compaq SmartArray 5302/64 hardware raid card > (ciss). The card hosts two arrays, one RAID-5 built from 4 discs that holds > the system and one RAID-0 built from 14 discs. All the discs are 36GB 10krpm > and I have one array on each channel on the card. > > Server #2: AthlonXP 2500+ with an old Maxtor 27GB UDMA66 disc for the > system. > > > What made me take notice was that server #2 ran through a "make > installkernel; make installworld" faster than server #1 during a recent > upgrade. This makes no sense given the superior I/O performance of the > hardware scsi raid array on server #1, and I know that in the past server #1 > has finished the process ahead of server #2. > > After the upgrade was done I ran some simple tests with 'dd', and it only > took ~1 minute for the system to live-lock. Breaking into DDB and killing > the 'dd' process brought the machine back to life. I assumed the problem was > ciss-related, CAM-related or SMP-related, but I just tried doing the same > thing on the UP machine (server #2), and it too live-locked within a minute. > > Both systems use pretty much the same config, with the only major difference > being SMP or not: > * SCHED_4BSD, PREEMPTION, ADAPTIVE_GIANT, DEVICE_POLLING, HZ=2000 > * debug.mpsafenet="1", debug.mpsafevfs="1" What happens if you turn off mpsafevfs? Scott
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