Sunday, 18 May 2014

smemstat: a new tool to report shared memory usage

Back in April I wrote smemstat in to dump out the per process shared memory usage based on the memory mapping data from /proc/$pid/smaps.   I tried to make smemstat as compact as possible with minimised changes in heap size to reduce the impact on the total system shared memory statistics.

smemstat reports the memory utilised per process taking in consideration pages that are shared with other processes. So, if two processes share 64K of memory, each process will report that memory as 32K each.

smemstat has to modes of operation: "dump all current memory stats" and a "dump periodic change in memory stats".  The former is useful for a single snapshot view of memory utilisation, where as the latter is useful to observe memory size changes over time. Exiting or new processes that share memory with other processes will cause a change the reported amounted of memory used by the processes because this memory is shared amongst a changed number of processes.

There are various options to smemstat, so consult the man page for more details.  One useful option is -o that collects the smemstat statistics into a JSON formatted output file. This can be useful for memory based tests as the structured JSON data can be easily parsed and analysed.

smemstat  has landed in Ubuntu Utopic 14.10 and is also available in Debian. Examples of smemstat can be found here. I hope it proves to be a useful utility.

No comments:

Post a comment