What each file means in linux/proc/sys/vm/

1)/proc/sys/vm/block_dump
This file indicates whether block debug mode is turned on to record all read-write and dirty block writeback actions.

Default setting: 0, disable block debug mode
2)/proc/sys/vm/dirty_background_ratio
This file represents the percentage of dirty data that reaches the overall system memory, triggering the pdflush process to write dirty data back to disk.

Default setting: 10
3)/proc/sys/vm/dirty_expire_centisecs
The file indicates that if the dirty data resides in memory longer than this value, the Pdflush process will write the data back to disk the next time.

Default setting: 3000 (1/100 sec)
4)/proc/sys/vm/dirty_ratio
This file indicates that if the dirty data generated by the process reaches the percentage of the system's overall memory, the process itself writes the dirty data back to disk.

Default setting: 40
5)/proc/sys/vm/dirty_writeback_centisecs
This file indicates how often the Pdflush process writes dirty data back to disk.

Default setting: 500 (1/100 sec)
6)/proc/sys/vm/vfs_cache_pressure
This file indicates that the kernel recycles the memory used by the directory and Inode caches, and the default value of 100 means that the kernel will keep the directory and inode caches at a reasonable percentage based on Pagecache and Swapcache. Lowering this value below 100 causes the kernel to tend to retain the directory and Inode caches, and increasing this value by more than 100 will cause the kernel to tend to reclaim the directory and Inode caches.

Default setting: 100
7)/proc/sys/vm/min_free_kbytes
This file represents the minimum amount of free memory (Kbytes) that the Linux VM is forced to keep.

Default setting: 724 (512M physical memory)
8)/proc/sys/vm/nr_pdflush_threads
This file represents the number of Pdflush processes currently running, and the kernel will automatically add more Pdflush processes with high I/O load.

Default setting: 2 (Read only)
9)/proc/sys/vm/overcommit_memory
This file specifies the kernel's policy for memory allocation, which can be 0, 1, 2.
0, indicates that the kernel will check for sufficient available memory to be used by the process, and if sufficient memory is available, the memory request is allowed; otherwise, the memory request fails and the error is returned to the application process.
1, which means that the kernel allows all physical memory to be allocated regardless of the current memory state.
2, which indicates that the kernel allows allocating more memory than the sum of all physical memory and swap space (refer to Overcommit_ratio).

Default setting: 0
)/proc/sys/vm/overcommit_ratio
The file indicates that if overcommit_memory=2, the percentage of memory that can be overloaded, the overall available memory of the system is calculated by the following formula.
System assignable Memory = Swap space + physical memory *overcommit_ratio/100

Default setting: 50 (%)
One)/proc/sys/vm/page-cluster
This file represents the number of pages written once to the swap area, 0 for 1 pages, 1 for 2 pages, and 2 for 4 pages.

Default setting: 3 (2 of 3 parties, 8 pages)
/proc/sys/vm/swapiness)
The file represents the degree to which the system is exchanging behavior, and the higher the value (0-100), the more likely the disk exchange will occur.

Default setting: 60
Legacy_va_layout)
This file indicates whether to use the latest 32-bit shared memory mmap () system calls, and how Linux supports shared memory allocations including mmap (), Posix,system VIPC.
0, use the latest 32-bit mmap () system call.
1, use the system call provided by the 2.4 kernel.

Default setting: 0
Nr_hugepages)
The file represents the number of hugetlb pages reserved by the system.
Hugetlb_shm_group)
This file represents the System group ID that allows the hugetlb page to be used to create systems VIPC shared memory segments.

What each file means in linux/proc/sys/vm/