Memory profiling is the process of dynamic program analysis to determine a program's memory consumption and identify ways to optimize it. In this recipe, we discuss how you can use memory profilers on the Ceph daemons for memory investigation.
- Start the memory profiler on a specific daemon:
# ceph tell osd.0 heap start_profiler - It's a good idea to keep the profiler running for a few hours so that it can collect as much information related to memory footprint as possible. At the same time, you can also generate some load on the cluster.
- Next, print heap statistics about the memory footprint that the profiler has collected:
# ceph tell osd.0 heap stats
- You can also dump heap stats on a file that can be used later; by default, it will create the dump file as
/var/log/ceph/osd.0.profile.0001.heap:# ceph tell osd.0 heap dump
- To read this dump file, you will require
google-perftools:# yum install -y google-perftools - To view the profiler logs:
# pprof --text {path-to-daemon} {log-path/filename} # pprof --text /usr/bin/ceph-osd /var/log/ceph/osd.0.profile.0001.heap
- For granule comparison, generate several profile dump files for the same daemon, and use the Google profiler tool to compare it:
# pprof --text --base /var/log/ceph/osd.0.profile.0001.heap /usr/bin/ceph-osd /var/log/ceph/osd.0.profile.0002.heap - Release memory that TCMALLOC has allocated but is not being used by Ceph:
# ceph tell osd.0 heap release - Once you are finished, stop the profiler:
# ceph tell osd.0 heap stop_profiler
The Ceph daemons process has matured much, and you might not really need memory profilers for analysis, unless you encounter a bug that's causing memory leaks. You can use the previously discussed procedure to figure out memory issues with the Ceph daemons.
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