2.5.2-pre performance degradation on an old 486

[Mikael Pettersson <mikpe@csd.uu.se>]

When running 2.5.2-pre7 on my old for-testing-only 486(*),
file-system accesses seem to come in distinct bursts preceded
by lengthy pauses. Overall performance is down quite significantly
compared to 2.4.18pre1 and 2.2.20pre2. To measure it I ran two
simple tests:

Test 1: time to boot the kernel, from hitting enter at the LILO
prompt to getting a login prompt
Test 2: time to "rm -rf" a clean linux-2.4.17 source tree, using
the newly booted kernel (no other access to the tree before that,
so it wasn't cached in any way, and the machine was otherwise idle)

		Test 1		Test 2
2.2.21pre2:	71 sec		 75 sec
2.4.18pre1:	64 sec		 72 sec
2.5.2-pre7:	97 sec		251 sec

I haven't noticed any slowdowns on my other boxes, so I didn't
do any measurements on them. On the 486 it's very very obvious.

/Mikael

(*) 100MHz 486DX4, 28MB ram, no L2 cache, two old and slow IDE disks,
small custom no-nonsense RedHat 7.2, kernels compiled with gcc 2.95.3.