slabtop
Real-time display of kernel slab memory cache information
Supplementary instructions
slabtop command displays the details of the kernel "slab" buffer in real time.
grammar
slabtop(option)Options
--delay=n, -d n: Update the displayed information every n seconds, the default is every 3 seconds;
--sort=S, -s S: Specify the sorting standard for sorting (for the sorting standard, refer to the following or the man manual);
--once, -o: Exit after displaying once;
--version, -V: display version;
--help: Display help information.Sorting criteria:
Knowledge expansion
When kernel modules allocate resources, in order to improve efficiency and resource utilization, they are allocated through slab. Through the slab information and the source code, you can get a rough understanding of the system's operation, such as whether there are abnormally many resources or whether there are any leaks. The Linux system exposes slab usage to users through /proc/slabinfo.
The slab allocator used by Linux is based on an algorithm first introduced by Jeff Bonwick for the SunOS operating system. Jeff's allocator is built around object caching. In the kernel, large amounts of memory are allocated for a limited set of objects, such as file descriptors and other common structures. Jeff found that the time required to initialize a normal object in the kernel exceeded the time required to allocate and deallocate it. Therefore, he concluded that memory should not be released back to a global memory pool, but should be kept in a state initialized for a specific purpose. The Linux slab allocator uses this idea and others to build a memory allocator that is efficient in both space and time.
The file that holds information about all active slab caches in the monitoring system is /proc/slabinfo.
Example
slabtop
Active / Total Objects (% used) : 897519 / 1245930 (72.0%)
Active / Total Slabs (% used) : 38605 / 38605 (100.0%)
Active / Total Caches (% used) : 94 / 145 (64.8%)
Active / Total Size (% used) : 129558.22K / 153432.58K (84.4%)
Minimum / Average / Maximum Object : 0.01K / 0.12K / 128.00K
OBJS ACTIVE USE OBJ SIZE SLABS OBJ/SLAB CACHE SIZE NAME
440136 171471 38% 0.05K 6113 72 24452K buffer_head
190086 148576 78% 0.05K 2437 78 9748K selinux_inode_security
151840 146366 96% 0.48K 18980 8 75920K ext3_inode_cache
144333 144143 99% 0.02K 711 203 2844K avtab_node
130529 128488 98% 0.13K 4501 29 18004K dentry_cache
99214 99071 99% 0.03K 878 113 3512K size-32
43834 28475 64% 0.27K 3131 14 12524K radix_tree_node
17818 9450 53% 0.06K 302 59 1208K size-64
4602 4562 99% 0.05K 59 78 236K sysfs_dir_cache
3220 2855 88% 0.08K 70 46 280K vm_area_struct
2460 2114 85% 0.12K 82 30 328K size-128
1564 1461 93% 0.04K 17 92 68K Acpi-Operand
1540 1540 100% 0.33K 140 11 560K inode_cache
1524 466 30% 0.01K 6 254 24K anon_vma
1440 515 35% 0.05K 20 72 80K avc_node
1440 1154 80% 0.19K 72 20 288K filp
1170 1023 87% 0.05K 15 78 60K ext3_xattr
845 724 85% 0.02K 5 169 20K Acpi-Namespace
638 315 49% 0.35K 58 11 232K proc_inode_cache
450 434 96% 0.25K 30 15 120K size-256
424 386 91% 0.50K 53 8 212K size-512
312 107 34% 0.05K 4 78 16K delayacct_cache
306 284 92% 0.43K 34 9 136K shmem_inode_cache
303 108 35% 0.04K 3 101 12K pid
300 261 87% 0.19K 15 20 60K skbuff_head_cache
300 300 100% 0.12K 10 30 40K bio
260 260 100% 32.00K 260 1 8320K size-32768
254 6 2% 0.01K 1 254 4K revoke_table
236 55 23% 0.06K 4 59 16K fs_cache
216 203 93% 1.00K 54 4 216K size-1024
214 214 100% 2.00K 107 2 428K size-2048
203 83 40% 0.02K 1 203 4K biovec-1
