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FromBill Metzenthen <>
SubjectAnother rust result
DateFri, 24 Jul 1998 20:09:54 +1000 (EST)
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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