For my Java apps with very long classpaths, I cannot see the main class specified near the end of the arg list when using ps. I think this stems from my Ubuntu system's size limit on /proc/pid/cmdline. How can I increase this limit?
8 Answers
You can't change this dynamically, the limit is hard-coded in the kernel to PAGE_SIZE in fs/proc/base.c:
274 int res = 0;
275 unsigned int len;
276 struct mm_struct *mm = get_task_mm(task);
277 if (!mm)
278 goto out;
279 if (!mm->arg_end)
280 goto out_mm; /* Shh! No looking before we're done */
281
282 len = mm->arg_end - mm->arg_start;
283
284 if (len > PAGE_SIZE)
285 len = PAGE_SIZE;
286
287 res = access_process_vm(task, mm->arg_start, buffer, len, 0);
I'm pretty sure that if you're actually seeing the arguments truncated in /proc/$pid/cmdline then you're actually exceeding the maximum argument length supported by the OS. As far as I can tell, in Linux, the size is limited to the memory page size. See "ps ww" length restriction for reference.
The only way to get around that would be to recompile the kernel. If you're interested in going that far to resolve this then you may find this post useful: "Argument list too long": Beyond Arguments and Limitations
Additional reference:
ARG_MAX, maximum length of arguments for a new process
Perhaps the 'w' parameter to ps is what you want. Add two 'w' for greater output. It tells ps to ignore the line width of the terminal.
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