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KernelTrap: Listing Threads in /proc

Feb 25, 2003, 04:00 (0 Talkback[s])

"The /proc directory on a Linux server is a virtual filesystem (procfs) providing an interface between the kernel, kernel modules, and user space processes. A quick 'ls -l /proc' reveals numerous apparently empty files, though a 'cat' of of these 'empty' files offers a wealth of interesting information generated by the kernel. (The kernel configuration option CONFIG_PROC_FS must be enabled)

"Within the /proc directory each running process has a subdirectory, each named an integer which is the process' ID (PID). Within these subdirectories are a number of files offering useful information about each process. For example, the file 'cmdline' (/proc//cmdline) shows the command line arguments passed to this process, and 'environ' (/proc//environ) shows all environment variables known to the process.

"Ingo Molnar recently posted a patch to the lkml resulting in a significant increase in threading performance when displaying individual threads within the /proc directory. His solution is to add a '.' to child-thread entries, thus hiding them unless there's a need to view them. He also adds a ''lookup cursor' cookie' for further optimization..."

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