I have posted this question in comp.os.linux.setup, and checked the
linux-kernel archives, but couldn't find anything relevant. I hope it's OK
to post this sort of query here, since I believe it must be a kernel
issue.
I have a Dual PII-350 on a Gigabyte GA-6BXDS motherboard, which has been
running happily with 512M RAM. I recently upped the memory from 4 x 128M
DIMM's to 4 x 256M DIMM's. I have been experiencing horrific performance
problems when using more than 512M of this memory. OS is Mandrake Linux
v5.3, which is virtually identical to Red Hat v5.3.
I have tried it using different amounts of memory (via append mem=):
512M, 768M, 900M and 1024M. I don't remove any of the DIMM's when setting
the amount of memory to use. I tried it with the following kernels:
2.0.36 - standard red hat
2.2.1 - standard red hat
2.2.3 - custom compiled
2.2.8 - custom compiled
2.2.9 - custom compiled
with __PAGE_OFFSET set to 0x80000000 to test with 1024M
I have tested performance by running updatedb immediately after boot. With
approx 105,000 files/dirs it normally takes 1m30 to complete. When it's
running slowly, it's approx 12m. The problem occurs with every kernel
above.
I found the following in the INFO-SHEET howto, section 3.3:
Some people (including Linux) hae noted that adding RAM without adding
more cache at the same time has slowed down their machines extremely,
so if you add memory and find your machine slower, try adding more
cache.
I assume that this refers to level 2 cache - AFAIK each PII has 512K of
Level 2 in the same casing as the processor, so adding additional cache
isn't an option.
One thing that I thought of but haven't had time to try yet was
recompiling a kernel without SMP support to see if this has any effect. Is
this worth it? Could it affect things?
I'd really like to get this machine running with 1024M, so if anyone has
any suggestions I'd love to hear them.
Please CC: any replies to my e-mail address, since I'm not on the list.
Thanks in advance,
-- Corin Hartland-Swann
-- Cthulhu Internet
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