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As I spawn several processes in a loop, I hit the maximum number of open files handles and the for loop breaks.

When I count the open file handles using lsof I get:

$ lsof | wc -l
1464377

However checking fs.file-nr returns:

$ sysctl fs.file-nr
fs.file-nr = 35328      0       6553201

I expected the first number to be 1464377.

I have a couple of questions:

  1. What's the difference between the output of lsof (1464377) and file-nr (35328).

  2. The maximum seems to be 6553201, which looks rather arbitrary. What's the maximum value for this number?

2

as per man lsof

An open file may be a regular file, a directory, a block special file, a character special file, an executing text reference, a library, a stream or a network file (Internet socket, NFS file or UNIX domain socket.) A specific file or all the files in a file system may be selected by path.

So number of line in lsof is likely much more than actual file descriptor.

See this reated question : https://serverfault.com/questions/485262/number-of-file-descriptors-different-between-proc-sys-fs-file-nr-and-proc-pi

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@Archemar is right. I'm late with answer. I check it (exclude character special file, network file, dirs ...):

$ lsof /|grep -v DIR|wc -l 
1191

$ sysctl fs.file-nr
fs.file-nr = 1280   0   98018

There are 1191 opened files and 1280 allocated handles. Values are very nearly.

Kernel documentation about fs partition on sysctl

  • True, I get closer values but they are still off by a factor of 3. grepped lsof giving me 11410 and file-nr giving me 32640. – Paulo Matos Mar 19 '18 at 7:28

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