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SubjectRe: good 2.1.x SMP kernel is? [possible smoking gun?]
12/31/98 @ 10:32:18 AM (Thursday)

Some more datapoints, and a possible smoking gun.

After 2.2.0-pre1 came out, I put the 2nd processor back into the machine
and crashed it about 20 times trying to catch it in the act.

The machine is stable, in general, if:

o Only one of the two CPUs is used
o You mount the partitions as sync (not good test; can't stress it)

Same (SMP) kernel, all other things held constant.


I spent most of yesterday trying to get it up on a serial console on the
theory that if it would spit out any messages on that, I wouldn't have them
disappear when the machine rebooted and/or otherwise froze. I never did
get it to output it to the console, but I did get one message on the VGA
console during one lockup (vs reboot):

swap_duplicate: entry 0b190000, offset exceeds max

Hmm. Swapping problems would happen while compiling but not under idle
use, so I tried to abuse that. I did repeated kernel builds under things
like -j32 and -j64 (both worked) where just -j failed (ran out of virtual
memory, didn't write down exact error; typical fork issue).

Since this tends to happen an hour+ into my build, perhaps memory needs
to be more scrambled by use to trigger the problem. I have never seen
my new box use much swap, but that isn't surprising since I now have more
memory than I used to have combined memory & swap.


As I said, my ASUS P2B-DS is an upgrade over my previous system. The
previous system had 64MB of RAM, then was later upgraded to 96MB. The
new system has 256MB. I did keep the old disk drive, and was using the
old swap partition:

Disk /dev/sdb: 255 heads, 63 sectors, 1106 cylinders
Units = cylinders of 16065 * 512 bytes

Device Boot Start End Blocks Id System
/dev/sdb6 326 338 104391 82 Linux swap

No swap on /dev/sda. Sized Ok for 64MB and still more than 96, but
less than 256. The only reason I'm using that is because it was there
already and it seemed better than having no swap at all (at the time).

That was ~2AM last night, so I did a swapoff -a and restarted the big
build. Got up this morning and it had finished it, no crashes (but
only one test; I rebuilt 6-9 times on one CPU before I decided that was
probably Ok).

Am I getting crashes because I have less swap than physical memory?

--- john

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