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SubjectAnother rust result
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Surprise! The official 2.1.110 appears to have cured the rusting! I
didn't believe my measurements when I saw them so I tried 2.1.110-pre3
again, then 2.1.110 once more and got consistent results. The down
side is that it appears to have made the "pre-rusting" performance as
bad as the "post-rusting"...


Bill Metzenthen


--------------------------------------------------------------------------
Rusting Effect Update.
------- ------ -------
[For those new to the effect, somewhere in the 2.1.xx kernel series
my low memory machine (8Mbyte) began to get sluggish after being
used for some time, due to lots of swapping. This excessive swapping
is reliably triggered by doing a 'find' on a directory which has lots
of files (a few tens of thousands) in sub-directories, etc. My test
consists of measuring the time taken to compile one of the kernel files
before and after doing such a find (fresh after re-booting).]

The results so far:
kernel approx rusting effect (compile time in
seconds before and after 'find')
2.0.33 38 --> 30 (improves!)
2.1.96 37 --> 263
2.1.98 43 --> 284
2.1.99 36 --> 100
2.1.100 38 --> 121
2.1.101 47 --> 152
2.1.102 48 --> 150
2.1.103 53 --> 168
2.1.106 57 --> 209
2.1.108 54 --> 200
2.1.109 51 --> 273
2.0.33 42 --> 34
2.1.109 46 --> 153 (1: 20 40 60 > freepages)
--> 108 (1: 2 min)
--> 75 (1: 15 min)
--> 80 (1: 60 min)
2.1.109 40 --> 117 (2: 20 25 30 > freepages)
--> 90 (2: 2 min)
2.1.40 46 --> 42
2.1.64 56 --> 600
2.1.109patched 55 --> 192 (3)
2.1.110pre3 39 --> 51
--> 61 (4: 2 min)
--> 51 (4: 25 min)
2.1.110 49 --> 50

Notes: (1) mm parameters set with: echo "20 40 60" > /proc/sys/vm/freepages
and then test repeated after the shown delays without rebooting
between.
(2) mm parameters set with: echo "20 25 30" > /proc/sys/vm/freepages
(3) Patch by Andi Kleen <ak@muc.de>.
(4) Test repeated after the shown delays without rebooting. There
appears to be no significant recovery effect.
Don't read too much into the precise figures. These results were
obtained over a period of months, during which various things have
changed (such as libraries, probably the compiler, etc). The first
2.0.33 result was obtained on 25 April, the last on 18th July.

All of the later kernels <= 2.1.109 show some (but not full) recovery
over time.

--
-----------------------------------------------------------------------------
Bill Metzenthen | See http://www.suburbia.net/~billm/ for information
billm@melbpc.org.au | on an 80x87 FPU emulator, using floating point
billm@suburbia.net | (particularly on Linux), and code for manipulating
Melbourne, Australia | the floating point environment on 80x86 Linux.
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