The text you quoted below is referring to Solaris 2.5 this changed some what in
newer versions though there are still issues. Adrian Cockcroft has an excellent
book on tuning Solaris called "Sun Performance and Tuning : Java and the Internet"
the second edition covers Solaris 2.6 and definitely covers this issue. Also there
is a little information here http://www.apache.org/docs/misc/descriptors.html. This
is also mentioned in the Solaris 2 FAQ
http://www.wins.uva.nl/pub/solaris/solaris2.html
Here is the books amazon reference if you want more information
http://www.amazon.com/exec/obidos/ASIN/0130952494/qid=929045590/sr=1-1/002-9965784-9559220
Kimbro Staken
Paul Shannon wrote:
> Bernie at talkcity.com gave me a great tip on working around the
> solaris problem with 'too many open files'. He said that
> adding these "tunables" to /etc/system did the trick:
>
> set rlim_fd_max=4096
> set rlim_fd_cur=1024
>
> However, I felt a little timid about adding those settings without
> first understanding them, so I checked around a bit. I found
> no mention of them in Sun's AnswerBook. A search of the web
> got me an exchange in SunWorld Online
>
> http://suncom.bilkent.edu.tr/sunworldonline/swol-07-1996/swol-07-letters.html
>
> The full text of this exchange is below, but the gist of the message
> is that it may be dangerous to use any values greater than
>
> set rlim_fd_max=1024
> set rlim_fd_cur=256
>
> For the full story, see below.
>
> - Paul
>
> ------------------------- copied from sunworldonline ----------------
>
> Adrian:
>
> The sysadmin before me has placed these two tunables in
> /etc/system. They were there for a Solaris 2.4 system that was being
> used as our main Web gateway.
>
> set rlim_fd_max=4096
> set rlim_fd_cur=1024
>
> We are running under 2.5 on an Ultrasparc/167 and 256 megs of RAM.
>
> My belief is that I need to get some good documentation on these
> things and that the file descriptors are automatically tuned under a
> 2.x system. Right?
>
> --Dru Nelson, Four11 Corp.
>
> Adrian Cockcroft responds: Those settings are likely to cause
> problems. I'd remove them completely.
>
> www.sun.com and other web servers that I have looked at do not have
> any need to increase the number of file descriptors per process. This
> is usually only an issue for Sybase databases that have lots of
> users. The default max value is 1024, the "select" system call breaks
> if you set it higher due to FD_SET being hard coded as a 1024 bit wide
> bitfield.
>
> set rlim_fd_max=1024
>
> The current defaults to 64, you can set it up to 256 safely, beyond
> that stdio library calls and SunOS 4 programs running in binary
> compatibility mode will eventually break.
>
> set rlim_fd_cur=256
>
> If a particular command needs more, use a shell script wrapper to
> start the command and put a limit descriptors XXX command in the
> script so it only applies to that process.
>
> You can get "silent" corruption of your program if you set these too
> big, as it writes off the end of fixed size arrays.
>
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>
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