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Much Slower than 7.2?

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Hello psyche-list,

I've got a large data compilation application. It takes in a very
large quantity of text data and produces a resulting binary file that
is about 1.3 GB. In the mean time, it holds on the order of 2 GB of
data in memory while operating on it to produce the output file.

Under Red Hat 7.2 with the 2.4.9-31 kernel, my data compiling machine
require about 6 hours and 50 minutes to do this operation.

Under Red Hat 8.0 with the 2.4.18-18.8.0 kernel, the same machine
requires just over 2 DAYS to perform the same operation.

According to /proc/meminfo, the machine has a total memory of
791080960 bytes. So, I am not surprised that I need to do a fair
amount of paging. In addition to a 2 GB swap partition, I created a
pair of 2 GB swap files, to handle any overload. But, as I recall,
this was the case under 7.2 as well.

I have not made any substantial changes to the code that performs the
data compile. I was wondering whether there had been some significant
change in the memory management system or something else that would
account for this.

Also, I just noticed that another RH 8.0 system in my office, set up
by someone else, has a 4 GB swap partition. The mkswap(8) man page
still says that the maximum useful size for the i386 architecture is
about 2 GB. Is the man page out-of-date, or are we wasting 2 GB of
disk space? The /proc/meminfo and /proc/swaps seem to be indicating
that all of it is there and available. ???



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