Re: [RFC] Optimization for use-once pages

From: Patrick Dreker (
Date: Tue Jul 24 2001 - 15:24:17 EST


Am Dienstag, 24. Juli 2001 18:48 schrieb Linus Torvalds:
> Please people, test this out extensively - I'd love to integrate it, but
> while it looks very sane I'd really like to hear of different peoples
> reactions to it under different loads.
I just decided to give this patch a try, as I have written a little
application which does some statistics over traces dumped by another program
by mmap()ing a large file and reading it sequentially. The trace file to be
analyzed is about 240 megs in size and consists of records each 249 bytes
long. The analysis program opens and the mmap()s the trace file doing some
small calculations on the data (basically it adds up fields from the records
to get overall values).

I have tested this on my Athlon 600 with 128 Megs of RAM, and it does not
make any difference whether I use plain 2.4.7 or 2.4.5-use-once. The program
always takes about 1 minute 6 seconds (+- 2 seconds) to complete, and the
machine starts swapping out stuff (thus I have omitted further stats like
vmstat output). I have just taken another look into my program to verify it
does not do something silly, like keeping old data around, but the program
cycle is always the same: copy a record from the mmap into a struct, perform
analysis, and copy next record. The struct is always reused for the next
struct (so there is only one struct at any time).

I can do further tests, if someone asks me to. I could even modify the
analysis program to check changes in behaviour...

> Linus


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