Monitoring

Linux Monitoring¶

Memory¶

free -m

List of availble memory and used memory before/after buffers and caches are taken into consideration.

Does not include the memory used for the kernel caches, i.e. Slab. This memory will contribute to the overall used memory but will not show against the process.

Show resident set size (RSS) and virtual memory size (VMZ) for processes, also lists the command.

ps -eo pid,rss,vsz,cmd

If you take the sum of RSS + Slab -Shared then it is roughly equivalent to used memory from free (-buffers, caches).

List the current memory usage with breakdowns:

cat /proc/meminfo

List the slab usage

cat /proc/slabinfo

For the above the size (Bytes) can be calculated by multiplying <num_objs> * <objsize>.

Also slabtop provides info on the used memory for slab.

slabtop

References¶

Droping kernel caches: https://linux-mm.org/Drop_Caches

Where is my memory: https://www.dedoimedo.com/computers/slabinfo.html

Redhat6 memory info: https://access.redhat.com/solutions/406773

Slabs: https://medium.com/@dhelios/memory-caches-and-slab-objects-c1de113ce235

pidstat¶

Show stats for a particular process including voluntary and non-volunatary context switches

pidstat -w -p <pid> <interval secs>

e.g. pidstat -w -p 1345 1

strace¶

Capture system calls for app

strace -c -f -p <pid>

-c = capture count -f = trace child processes

To exit after a specific time period

timeout <secs> strace -c -f -p <pid>

count threads¶

Count the number of threads for a process

cat /proc/<pid>/status

There is the list is threads or

cat /proc/<pid>/status | grep -i threads

disk io latency¶

iostat -dxt 1 sdb

Check env for processes¶

Find the process id then

strings /proc/<pid>/environ

or

cat /proc/28818/environ | tr '\0' '\n'