Linux – the size of shared memory page

linuxmemory

On Linux, for each process, I can check /proc/PID/statm file.

It's numbers contain values of:

Total program size, in kilobytes
Size of memory portions, in kilobytes ??????
Number of pages that are shared

Which is great, but how do I know how much is a page?

Best Answer

I'm not a Linux god (by any means) but typically page sizes are 4Kb. There's a pagesize command that should tell you what it is set to on your system. This gives the output of the getpagesize() function.

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Linux – How to determine the memory used by a forked process (Linux)

Proportional set size is probably the best figure of memory use per-process you have available. It's the unique set size + (the shared pages / # of processes sharing).

So one process has used 44176 pages, of which 19388 are unique to that process. This means that 24788 are shared with others.

Looking at PSS as USS + (shared weight). The weight in this case is 8193, which is the proportion of shared memory pages (24788) attributable to this process. The more instances of an application you have sharing pages, the lower the weight for each process.

You can sum PSS across multiple processes and you won't count shared pages more than once. You can't, however, sum USS and PSS and expect RSS because PSS already includes USS.

Linux Bash – How to Sort du -h Output by Size

As of GNU coreutils 7.5 released in August 2009, sort allows a -h parameter, which allows numeric suffixes of the kind produced by du -h:

du -hs * | sort -h

If you are using a sort that does not support -h, you can install GNU Coreutils. E.g. on an older Mac OS X:

brew install coreutils
du -hs * | gsort -h

From sort manual:

-h, --human-numeric-sort compare human readable numbers (e.g., 2K 1G)

Best Answer

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Linux – How to determine the memory used by a forked process (Linux)

Linux Bash – How to Sort du -h Output by Size

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