vmalloc failures can already happen if you start 32 processes on i386 kernels,
each of them wanting to open file handle number 600.000 (if their
RLIMIT_NOFILE >= 600000)
fcntl(0, F_DUPFD, 600000);
We are not going to add warnings about vmalloc on every sysctl around there
that could allow a root user to exhaust vmalloc space. This is a vmalloc issue
on 32bit kernel, and quite frankly I never hit this limit.
If you take a look at vmalloc() implementation, fact that it uses a 'struct
vm_struct *vmlist;' to track all active zones show that vmalloc() is not used
that much.
NR_OPEN is the max value that RLIMIT_NOFILE can reach, nothing more.
You can set it to 256*1024*1024 or 4*1024 it wont change memory needs on your
machine, unless you raise RLIMIT_NOFILE and one of your program leaks file
handles, or really want to open simultaneously many of them.
Most programs wont open more than 500 files, so their file table is allocated
via kmalloc()
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