netdata/collectors/debugfs.plugin

OS provided metrics (debugfs.plugin)

debugfs.plugin gathers metrics from the /sys/kernel/debug folder on Linux systems. Debugfs exists as an easy way for kernel developers to make information available to user space.

This plugin is external, the netdata daemon spawns it as a long-running independent process.

In detail, it collects metrics from:

• /sys/kernel/debug/extfrag (Memory fragmentation index for each order and zone).
• /sys/kernel/debug/zswap (Zswap performance statistics).

Prerequisites

Permissions

No user action required.

The debugfs root directory is accessible only to the root user by default. Netdata uses Linux Capabilities to give the plugin access to debugfs. CAP_DAC_READ_SEARCH is added automatically during installation. This capability allows bypassing file read permission checks and directory read and execute permission checks. If file capabilities are not usable, then the plugin is instead installed with the SUID bit set in permissions so that it runs as root.

Metrics

Metric	Scope	Dimensions	Units	Labels
mem.fragmentation_index_dma	numa node	order0, order1, order2, order3, order4, order5, order6, order7, order8, order9, order10	index	numa_node
mem.fragmentation_index_dma32	numa node	order0, order1, order2, order3, order4, order5, order6, order7, order8, order9, order10	index	numa_node
mem.fragmentation_index_normal	numa node	order0, order1, order2, order3, order4, order5, order6, order7, order8, order9, order10	index	numa_node
system.zswap_pool_compression_ratio		compression_ratio	ratio
system.zswap_pool_compressed_size		compressed_size	bytes
system.zswap_pool_raw_size		uncompressed_size	bytes
system.zswap_rejections		compress_poor, kmemcache_fail, alloc_fail, reclaim_fail	rejections/s
system.zswap_pool_limit_hit		limit	events/s
system.zswap_written_back_raw_bytes		written_back	bytes/s
system.zswap_same_filled_raw_size		same_filled	bytes
system.zswap_duplicate_entry		entries	entries/s

Troubleshooting

To troubleshoot issues with the collector, run the debugfs.plugin in the terminal. The output should give you clues as to why the collector isn't working.

• Navigate to the plugins.d directory, usually at /usr/libexec/netdata/plugins.d/. If that's not the case on your system, open netdata.conf and look for the plugins setting under [directories].

  cd /usr/libexec/netdata/plugins.d/
  

• Switch to the netdata user.

  sudo -u netdata -s
  

• Run the debugfs.plugin to debug the collector:

  ./debugfs.plugin