Comment by jonasn
9 hours ago
You are spot on that the original author had a valid reason: at the time, it was literally the only way to do it.
The method in question (Java 1.5) was released in September 2004. While the POSIX standard existed, it only provided a way to get total CPU time, not the specific user time that Java needed. You can read about it more in the history section here: https://norlinder.nu/posts/User-CPU-Time-JVM/#a-walk-through....
But it's worth noting that while this specific case can be "fixed" with a function call, parsing /proc is still the standard way to get data in Linux.
Even today, a vast amount of kernel telemetry is only exposed via the filesystem. If you look at the source code for tools like htop, they are still busy parsing text files from /proc to get memory stats (/proc/meminfo), network I/O, or per-process limits. See here https://github.com/hishamhm/htop/blob/master/linux/LinuxProc....
That sounds like a pretty good reason!
I knew about using proc for all that other information. I just wouldn’t have imagined using it for critical performance path. Unless, that is, that’s the way you have to get the information.