[系统资源]/proc/meminfo和free输出解释

High Level statistics

RHEL 5, RHEL 6 and RHEL 7

MemTotal: Total usable memory
MemFree: The amount of physical memorynot used by the system
Buffers: Memory in buffer cache, so relatively temporary storage for raw disk blocks. This shouldn't get very large.
Cached: Memory in the pagecache (Diskcache and Shared Memory)
SwapCached: Memory that is present within main memory, but also in the swapfile. (If memory is needed this area does not need to be swapped out AGAIN because it is already in the swapfile. This saves I/O and increases performance if machine runs short on memory.)

RHEL 7 only

MemAvailable: An estimate of how much memory is available for starting new applications, without swapping.

Detailed Level statistics

RHEL 5, RHEL 6 and RHEL 7

Active: Memory that has been used more recently and usually not swapped out or reclaimed
Inactive: Memory that has not been used recently and can be swapped out or reclaimed
RHEL 6 and RHEL 7 only

Active(anon): Anonymous memory that has been used more recently and usually not swapped out
Inactive(anon): Anonymous memory that has not been used recently and can be swapped out
Active(file): Pagecache memory that has been used more recently and usually not reclaimed until needed
Inactive(file): Pagecache memory that can be reclaimed without huge performance impact
Unevictable: Unevictable pages can't be swapped out for a variety of reasons
Mlocked: Pages locked to memory using the mlock() system call. Mlocked pages are also Unevictable.

Memory statistics

RHEL 5, RHEL 6 and RHEL 7

SwapTotal: Total swap space available
SwapFree: The remaining swap space available
Dirty: Memory waiting to be written back to disk
Writeback: Memory which is actively being written back to disk
AnonPages: Non-file backed pages mapped into userspace page tables
Mapped: Files which have been mmaped, such as libraries
Slab: In-kernel data structures cache
PageTables: Amount of memory dedicated to the lowest level of page tables. This can increase to a high value if a lot of processes are attached to the same shared memory segment.
NFS_Unstable: NFS pages sent to the server, but not yet commited to the storage
Bounce: Memory used for block device bounce buffers
CommitLimit: Based on the overcommit ratio (vm.overcommit_ratio), this is the total amount of memory currently available to be allocated on the system. This limit is only adhered to if strict overcommit accounting is enabled (mode 2 in vm.overcommit_memory).
Committed_AS: The amount of memory presently allocated on the system. The committed memory is a sum of all of the memory which has been allocated by processes, even if it has not been "used" by them as of yet.
VmallocTotal: total size of vmalloc memory area
VmallocUsed: amount of vmalloc area which is used
VmallocChunk: largest contiguous block of vmalloc area which is free
HugePages_Total: Number of hugepages being allocated by the kernel (Defined with vm.nr_hugepages)
HugePages_Free: The number of hugepages not being allocated by a process
HugePages_Rsvd: The number of hugepages for which a commitment to allocate from the pool has been made, but no allocation has yet been made.
Hugepagesize: The size of a hugepage (usually 2MB on an Intel based system)

RHEL 6 and RHEL 7 only

Shmem: Total used shared memory (shared between several processes, thus including RAM disks, SYS-V-IPC and BSD like SHMEM)
SReclaimable: The part of the Slab that might be reclaimed (such as caches)
SUnreclaim: The part of the Slab that can't be reclaimed under memory pressure
KernelStack: The memory the kernel stack uses. This is not reclaimable.
WritebackTmp: Memory used by FUSE for temporary writeback buffers
HardwareCorrupted: The amount of RAM the kernel identified as corrupted / not working
AnonHugePages: Non-file backed huge pages mapped into userspace page tables
HugePages_Surp: The number of hugepages in the pool above the value in vm.nr_hugepages. The maximum number of surplus hugepages is controlled by vm.nr_overcommit_hugepages.
DirectMap4k: The amount of memory being mapped to standard 4k pages
DirectMap2M: The amount of memory being mapped to hugepages (usually 2MB in size)