Messages in this thread | | | From | F Harvell <> | Subject | 2.1.99 SMP w/md - utterly broken | Date | Fri, 01 May 1998 16:07:26 -0300 |
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From reading the list, it appeared that the 2.1.99 pre's and final were solving many of the IRQ/SCSI disk problems. I wasn't having any luck. I didn't say anything because I had recently upgraded my cpu's from Dual PPro 150 to Dual PPro 200 and my problems had gotten worse. I wasn't sure that I wasn't seeing a hardware problem.
Well, I finally got tired of the constant hung processes, crashes, and unreliability and decided to try and move my md 0 striped partitions back to standard partitions. I haven't had a problem since.
In hindsight, while I'm not particularly kernel savvy, I can guess from what I've read on the list that all of the sti(), cli(), save_flags(), and restore_flags() calls in the md.c code are not particularly SMP friendly. (Actually, I was having a bad time running a UP kernel as well.) I would highly recommend _not_ using md with any of the IO-APIC enabled kernels (2.1.85+) with an SMP system until md is brought into the bright new spin_lock()'ed future.
Also, a few observations:
a) the problems tend to show up (using ps ax) as processes stuck in the "D" state.
b) the update process can get stuck which will lead into a death spiral where, eventually, every process gets stuck and nothing can be done on the box.
c) the system speed does make a difference, i.e., it shows up much faster on PPro 200's than on PPro 150's.
d) When running with md, I constantly saw processes going into and out of the "D" state, without md, it only happens rarely. (while true; do ps axlw | grep D; sleep 1; done)
e) when md was running, the whole system was substantially slower than without it. I would guess that this is related to (d) as there were probably missed interrupts, etc.
If anyone else is already looking into the md problems, please let me know.
-- Mr. F Harvell Phone:407 696-4340 FTS International, Systems Division Phone:407 399-0342 (cell) 3498 Buffam Place Fax:407 696-4244 Casselberry, FL 32707 mailto:fharvell@fts.net
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