You can directly inspect kernel slab allocator statistics (/proc/slabinfo file) for detailed information on buffer, inode, dentry, or other caches in the Linux kernel, though slabtop utility will sort and pretty-print information in real-time.
Display kernel slab cache information in real-time.
$ sudo slabtop
Active / Total Objects (% used) : 5574868 / 8454157 (65.9%) Active / Total Slabs (% used) : 212861 / 212861 (100.0%) Active / Total Caches (% used) : 163 / 213 (76.5%) Active / Total Size (% used) : 1521776.41K / 2139878.34K (71.1%) Minimum / Average / Maximum Object : 0.01K / 0.25K / 16.75K OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME 872640 275998 31% 0.06K 13635 64 54540K kmalloc-64 580839 467151 80% 0.19K 27659 21 110636K dentry 497370 312123 62% 0.13K 16579 30 66316K kernfs_node_cache 476160 227988 47% 0.01K 930 512 3720K kmalloc-8 367536 199830 54% 0.32K 15314 24 122512K arc_buf_hdr_t_full 359096 135329 37% 0.50K 11224 32 179584K kmalloc-512 331149 293965 88% 0.10K 8491 39 33964K buffer_head 309952 307060 99% 0.06K 4843 64 19372K anon_vma_chain 262210 93833 35% 0.30K 10086 26 80688K dmu_buf_impl_t 249942 73835 29% 0.09K 5951 42 23804K kmalloc-96 248076 245056 98% 0.20K 6364 39 50912K vm_area_struct 234906 96505 41% 0.04K 2303 102 9212K abd_t 192675 83164 43% 0.57K 6885 28 110160K radix_tree_node 189016 122528 64% 0.89K 5404 35 172928K dnode_t 187266 186347 99% 0.09K 4071 46 16284K anon_vma 148208 142719 96% 0.25K 4632 32 37056K filp 135072 64696 47% 0.07K 2412 56 9648K range_seg_cache 126464 111974 88% 0.06K 1976 64 7904K kmalloc-rcl-64 98566 94311 95% 0.59K 3791 26 60656K inode_cache 97020 58211 59% 0.24K 2940 33 23520K sa_cache 92423 56600 61% 1.08K 3187 29 101984K zfs_znode_cache 70434 65366 92% 0.09K 1677 42 6708K kmalloc-rcl-96 67328 65750 97% 0.02K 263 256 1052K kmalloc-16 57420 42423 73% 1.07K 1980 29 63360K ext4_inode_cache 55440 54669 98% 0.19K 2640 21 10560K kmalloc-192 [...]
Display kernel slab cache information once, sorted by the cache size, and print the first twenty lines.
$ sudo slabtop --once --sort c | head -20
Active / Total Objects (% used) : 5571460 / 8454136 (65.9%) Active / Total Slabs (% used) : 212830 / 212830 (100.0%) Active / Total Caches (% used) : 163 / 213 (76.5%) Active / Total Size (% used) : 1521610.64K / 2139599.28K (71.1%) Minimum / Average / Maximum Object : 0.01K / 0.25K / 16.75K OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME 359096 135798 37% 0.50K 11224 32 179584K kmalloc-512 189016 122601 64% 0.89K 5404 35 172928K dnode_t 9230 7718 83% 16.00K 4615 2 147680K zio_buf_16384 367536 199836 54% 0.32K 15314 24 122512K arc_buf_hdr_t_full 580839 467091 80% 0.19K 27659 21 110636K dentry 192675 83190 43% 0.57K 6885 28 110160K radix_tree_node 92423 56600 61% 1.08K 3187 29 101984K zfs_znode_cache 20320 19887 97% 4.00K 2540 8 81280K kmalloc-4k 262210 93870 35% 0.30K 10086 26 80688K dmu_buf_impl_t 9857 6965 70% 8.00K 2465 4 78880K kmalloc-8k 497370 312123 62% 0.13K 16579 30 66316K kernfs_node_cache 57420 42423 73% 1.07K 1980 29 63360K ext4_inode_cache 98566 94311 95% 0.59K 3791 26 60656K inode_cache
Display usage information.
$ slabtop --help
Usage: slabtop [options] Options: -d, --delay <secs> delay updates -o, --once only display once, then exit -s, --sort <char> specify sort criteria by character (see below) -h, --help display this help and exit -V, --version output version information and exit The following are valid sort criteria: a: sort by number of active objects b: sort by objects per slab c: sort by cache size l: sort by number of slabs v: sort by number of active slabs n: sort by name o: sort by number of objects (the default) p: sort by pages per slab s: sort by object size u: sort by cache utilization For more details see slabtop(1).