Re: How to increat [sic.] max open files?

Richard B. Johnson (
Fri, 3 Jan 1997 11:51:31 -0500 (EST)

> I run into the 256 fd limit all the time. I've written several
> multi-threaded servers that are *designed* to handle several thousand
> connections from several thousand clients at once. To test how many
> connections these servers can handle, I need a process to *open* several
> thousand connections to it.
> Eric
The number 256 does certainly look like a "made up" number, as abitrary
as they come. But, my point is that if the number was 1024 or 1.84e19,
the number would be "wrong". I have a server that handles all the
source-code access in the whole company. When it runs out of resources,
it makes another process, etc. The limit becomes the amount or RAM and
or page-file. I didn't write the code so I am not blowing my own horn.
The code was written by someone who was used to the limited resources
of a VAX, then ported to Suns. I ported it to Linux by simply compiling
and fixing a few "includes".

The problems with limits, whether artifical or not, is that they always
exist. In 1967, there was the first need to "sort" a telephone directory
on a machine (IBM 360) with 4k or real core. A procedure was designed,
called the "Chicago Sort" (it was the Chicago telephone database). The
designer knew that you only had to have two strings in memory at any one
time, therefore RAM was not a problem.

If someone in the nineties was given the task, they would state; "It
can't be done because...". And they would claim that the entire database
would have to be present in RAM all at once, etc. This is because we
have gotten used to "unlimited" resources and many have written code that
needs such an environment. A bit more design before writing, would not
only remove potential problems, but probably result in a lot better
performance of many shared-resource applications such as servers.

In the network example above, it is possible, with very little extra
code, to "fail-over" to another machine if all the resources of the
original machine are becoming exhausted. This is entirely transparent
to the client being served.

But, you have to test an existing server that was not completely designed
before it was implemented. Note I am not implying anything bad, only
making an observation. I see on the "net" some changes are being made to
the system calls that crash when you modify the header files to use more
FDs. My guess is that the artificial limit will be raised, then raised,
then raised, etc.....

Dick Johnson
Richard B. Johnson
Project Engineer
Analogic Corporation
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