Hello,
After the last patch I submitted with regarding to /etc/services,
I was asked if I could see if I could do something about the speed
of it. Personally I don't worry too much about it, my programs only
access getservbyname() only once per program :-)
I did some tests with it, and at this moment you got the speed for
telnet/tcp, which lives at the beginning of /etc/services:
telnet/tcp
1 times - 0.000369 seconds
10 times - 0.000583
100 times - 0.006279
1000 times - 0.059566
10000 times - 0.590499
100000 times - 5.591417
And dbbrowse/tcp, which lives at the end of /etc/services
dbbrowse/tcp
1 times - 0.001748 seconds
10 times - 0.011674
100 times - 0.117460
1000 times - 1.172199
10000 times - 11.966367
100000 times - 120
So... what can we do?
- Instead of reading and parsing /etc/services every time, read it
only once and use a cached version for all further getservbyxxx()
calls. This has a startup-penalty (once per application) and a
memory penalty, but all next calls are faster, specially for
services at the end of /etc/services.
- Instead of reading and parsing /etc/services every time, use a
hash or btree file a la the aliases database. A hash one (first
key, next key) could be a replacement to use with getservent(),
while a btree one could be be a replacement to use with getservbyname().
This doesn't have the startup-penalty, but the sysadmin needs to
keep track of changes in /etc/services and needs to rebuild it.
- Instead of reading and parsing /etc/services every time, open a
socket and ask a daemon for the information. Which daemon is a
good question, but it can automatically re-read the /etc/services
file if it got changed.
Other things to worry(?) about are YP/NIS. From what I've seen in
getservent() is that is happily intertwined with the /etc/services
code.
Anybody with comments or suggestions from earlier threads like this?
Edwin
--
Edwin Groothuis | Personal website: http://www.mavetju.org
[EMAIL PROTECTED] | Weblog: http://www.mavetju.org/weblog/
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