linux-kernel - too low MAX_MP

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Message-ID: <20060731115545.GA3292@pc11.op.pod.cz>
Date:	Mon, 31 Jul 2006 13:55:45 +0200
From:	Vitezslav Samel <samel@...l.cz>
To:	linux-kernel@...r.kernel.org
Subject: too low MAX_MP_BUSSES

	Hi!

  I tried upgrading our server (i386 arch) from 2.6.16 to 2.6.17 but there
were some odd messages in dmesg:

	MP table busid value (32) for bustype ISA is too large, max. supported is 31

and (repeated 315 times):

	unknown bus type 32

I found out that 50% of the processor time was spent in softirq and the timers
ran too fast. I didn't look for what else was wrong.

  Tracked down to this change in 2.6.17-rc2:

diff -urN linux-2.6.17-rc1/arch/i386/kernel/mpparse.c linux-2.6.17-rc2/arch/i386/kernel/mpparse.c
+       if (m->mpc_busid >= MAX_MP_BUSSES) {
+               printk(KERN_WARNING "MP table busid value (%d) for bustype %s "
+                       " is too large, max. supported is %d\n",
+                       m->mpc_busid, str, MAX_MP_BUSSES - 1);
+               return;
+       }

 Uping the MAX_MP_BUSSES value in include/asm-i386/mach-default/mach_mpspec.h
to 64 makes the machine work O.K.
The system is HP DL380 g4 with 1 Xeon CPU, kernel compiled non-SMP.

  Here is excerpt from mptable output:
---
Bus:            Bus ID  Type
                 0       PCI
                 1       PCI
                 2       PCI
                 3       PCI
                 4       PCI
                 5       PCI
                 6       PCI
                10       PCI
                32       ISA
---
The last item is the offending one.

Please, can you consider up the default value of MAX_MP_BUSSES?

P.S.: also tested 2.6.18-rc3, the same - bad - result

	Cheers,
		Vita
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