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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