Why Do `docker stats` and `Go Tool Pprof` Show Different Memory Usage?

Memory Discrepancy between 'docker stats' and 'Go Tool Pprof'

While investigating a suspected memory leak in a Go application running within Docker, a developer observed a discrepancy between the memory usage reported by 'docker stats' and the results obtained from 'Go Tool Pprof'.

Docker Stats:

'docker stats' displays memory usage statistics from the container's cgroups. It includes both used memory and memory allocated for caching (Page Cache and RES). As a result, the reported memory usage may not reflect the exact amount of memory being used by the application.

'Go Tool Pprof':

'Go Tool Pprof' provides detailed information about the memory heap of the running application. It shows the amount of allocated and in-use memory, excluding the Page Cache and RES.

Possible Explanation for Discrepancy:

The 'Memory used' metric reported by 'docker stats' includes cached data, while 'Go Tool Pprof' only shows the memory directly used by the application. Therefore, it is possible that the apparent increase in memory usage reported by 'docker stats' is actually due to caching behavior.

Memory Limit Setting:

By setting a memory limit for the container in 'docker-compose.yml', the developer can control the maximum amount of memory that the application can use. This helps prevent the container from exceeding its memory allocation and potentially causing an OOM (out of memory) error. To set a memory limit, add the following line to the service configuration in 'docker-compose.yml':

mem_limit: 32m

Conclusion:

The discrepancy between the memory usage reported by 'docker stats' and 'Go Tool Pprof' is likely due to the different metrics being measured. 'Go Tool Pprof' provides a more accurate representation of the memory actually used by the application, while 'docker stats' includes cached data as well. By setting a memory limit in 'docker-compose.yml', the developer can control the container's memory usage and limit the chances of encountering OOM errors.

The above is the detailed content of Why Do `docker stats` and `Go Tool Pprof` Show Different Memory Usage?. For more information, please follow other related articles on the PHP Chinese website!