/proc/slabinfo gives information about memory usage on the slab level. Linux kernels uses slab pools to manage memory above the page level. Commonly used objects have their own slab pools. Instead of parsing the highly verbose /proc/slabinfo file manually, the /usr/bin/slabtop program displays kernel slab cache information in real time. This program allows for custom configurations, including column sorting and screen refreshing.
Sample slabtop :
# /usr/bin/slaptop
Active / Total Objects (% used) : 286703 / 730599 (39.2%)
Active / Total Slabs (% used) : 46347 / 46357 (100.0%)
Active / Total Caches (% used) : 95 / 142 (66.9%)
Active / Total Size (% used) : 89858.38K / 179248.09K (50.1%)
Minimum / Average / Maximum Object : 0.01K / 0.25K / 128.00K
OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME
279330 86167 30% 0.25K 18622 15 74488K size-256
88046 44665 50% 0.27K 6289 14 25156K radix_tree_node
79350 3621 4% 0.05K 1058 75 4232K buffer_head
71266 32169 45% 0.15K 2741 26 10964K dentry_cache
…
Important parameters in /proc/slabinfo & slaptop are as below :
- OBJS — The total number of objects (memory blocks), including those in use (allocated), and some spares not in use.
- ACTIVE — The number of objects (memory blocks) that are in use (allocated).
- USE — Percentage of total objects that are active. ((ACTIVE/OBJS)(100))
- OBJ SIZE — The size of the objects.
- SLABS — The total number of slabs.
- OBJ/SLAB — The number of objects that fit into a slab.
- CACHE SIZE — The cache size of the slab.
- NAME — The name of the slab.