Linux's problems with too much memory - summary /2

Pavel Machek (
Sun, 27 Apr 1997 14:02:58 +0200


I'm sorry for posting so much but looks like this is definitely
_not_ hardware problem.

My linux on AMD 486DX2/80, 128k l2 cache slows down quite a bit when I
go from 16M to 20M. Memory is one 16MB, 72-pin simm and one 4MB,
72-pin simm.

It is *not* cache problem (present even with l2 disabled).
It is *not* interleaving problem. Why do I think so?

Compile times (compile of 2.1.36 kernel):

mem=20M - 30 minutes
mem=16M - 22 minutes
[well, that proves nothing, but look at following]
mem=16490k - 22 minutes
mem=16800k - 29.8 minutes
mem=17M - 30 minutes

If it was interleave problem, there should be *big* difference
between 17M and 20M. It is not.

Someone suggested that some tables grow quite a bit when going from
<16M to >16M. It's strange that 16400k is still fast... And that
bigger tables might be bigger than some cache...

Could someone with 486 (or with pentium & 4M pages disabled) try going
to <16M and look at times?

I'm really 	   Pavel
Look at ;-).