在Linux下可以使用/proc/meminfo文件查看操作系統內存的使用狀態
# cat /proc/meminfo MemTotal: 16333852 kB MemFree: 1633564 kB Buffers: 212448 kB Cached: 4422808 kB SwapCached: 0 kB Active: 10343096 kB Inactive: 3784128 kB Active(anon): 7954776 kB Inactive(anon): 1537404 kB Active(file): 2388320 kB Inactive(file): 2246724 kB Unevictable: 0 kB Mlocked: 0 kB SwapTotal: 2047992 kB SwapFree: 2047992 kB Dirty: 672 kB Writeback: 0 kB AnonPages: 9491968 kB Mapped: 34240 kB Shmem: 212 kB Slab: 375180 kB SReclaimable: 316296 kB SUnreclaim: 58884 kB KernelStack: 27456 kB PageTables: 35396 kB NFS_Unstable: 0 kB Bounce: 0 kB WritebackTmp: 0 kB CommitLimit: 10214916 kB Committed_AS: 19743752 kB VmallocTotal: 34359738367 kB VmallocUsed: 303556 kB VmallocChunk: 34359420140 kB HardwareCorrupted: 0 kB AnonHugePages: 0 kB HugePages_Total: 0 HugePages_Free: 0 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB DirectMap4k: 10240 kB DirectMap2M: 16766976 kB
注意這個文件顯示的單位是kB而不是KB，1kB=1000B,但是實際上應該是KB，1KB=1024B
這個顯示是不精確的，是一個已知的沒有被更正的歷史遺留問題。因爲很多程序依賴這個文件查看內存使用的是kB字符
MemTotal: 16333852 kB
MemTotal是可使用內存的總量，單位是KB，物理內存減去一些保留內存和內核二進制代碼佔用的內存
MemFree: 1633564 kB
MemFree 剩下沒有被使用的物理內存，單位是kibibytes，即KB
Buffers: 212448 kB
Buffers 臨時存儲原始磁盤塊的總量，單位是KB
Cached: 4422808 kB
Cached 用作緩存內存的物理內存總量，單位是KB
SwapCached: 0 kB
SwapCached 曾經被移入到swap，然後又回到主內存，但是仍然也在swapfile中保留的總內存大小。這樣可以節省I/O，應爲內存不需要再移入到swap
Active: 10343096 kB
Active 最近經常被使用的內存大小總量，單位是KB。
Inactive: 3784128 kB
Inactive 最近不是經常使用的內存，單位是KB
Active(anon): 7954776 kB
匿名和tmpfs/shmem內存總量，單位是KB. 自上次系統移動一些什麼東西到swap後處於活動使用狀態或者之前處於活動使用狀態的內存
Inactive(anon): 1537404 kB
作爲候選收回的匿名和tmpfs/shmen內存總量，單位是KB
Active(file): 2388320 kB
文件緩存內存的總量，單位是KB。處於活動使用狀態，或者之前自上次系統召回內存處於活動使用狀態的內存
Unevictable: 0 kB
The amount of memeory,in kibibytes,discovered by the pageout code,that is not evictable because it is locked into memeory by user programs.
Mlocked: 0 kB
因爲被用戶程序鎖住不能被回收的內存總量，單位是KB
SwapTotal：
swap總量，單位是KB
SwapFree：
空閒swap總量
Dirty 等待寫回到磁盤內存總量，單位是KB
Writeback 正在寫回到磁盤的內存總量，單位是KB
AnonPages The total amount of memory,in kibibytes,used by pages that are not backed by files and are mapped into userspace page tables
Mapped The memory,in kibibytes, used for files that have been mmaped,such as libraries
Shmem The total amount of memeory,in kibibytes,used by shared memeory(shmem) and tmpfs
Slab The total amount of memeory,in kibibytes,used by the kernel to cache data structures for its own use.
SReclaimable The part of Slab that can be reclaimed,such as caches.
SUnreclaim The part of Slab that cannot be reclaimed even when lacking memeory
KernelStack The amount of memeory,in kibibytes,used by the kernel stack allocations done for each task in the system
PageTables The total amount of memeory,in kibibytes,dedicated to the lowest page table level.
NFS_Unstable The amount,in kibibytes,of NFS page sent to the server but not yet committed to the stable storage
Bounce The amount of memory,in kibibytes,used for the block device "bounce buffers"
WritebackTmp The amount of memory,in kibibytes, used by FUSE for temporary writeback buffers
CommitLimit The total amount of memory currently avaiable to be allocated on the system based on the overcommit ratio(vm.overcommit_ratio) This limit is only adhered of if stric overcommit accounting is enabled(mode 2 in vm.overcommit_memory)
([total RAM pages] - [total huge TLB pages]) * overcommit_ratio ───────────────────────────────────────────────────────────────── + [total swap pages] 100
例如1G的物理內存和7GB的swap內存，vm.overcommit_ratio設置爲30，那麼CommitLimit 就是7.3GB
Committed_AS The total amount of memory,in kibibytes,estimated to complete the workload.
This value repsents the worst case scenario value,and also includes swap memory
VMallocTotal The total amount of memory,in kibibytes,of total allocated virtual address space
VMallocUsed — The total amount of memory, in kibibytes, of used virtual address space.
VMallocChunk — The largest contiguous block of memory, in kibibytes, of available virtual address space.
HardwareCorrupted — The amount of memory, in kibibytes, with physical memory corruption problems, identified by the hardware and set aside by the kernel so it does not get used.
AnonHugePages — The total amount of memory, in kibibytes, used by huge pages that are not backed by files and are mapped into userspace page tables.
HugePages_Total — The total number of hugepages for the system. The number is derived by dividing Hugepagesize by the megabytes set aside for hugepages specified in /proc/sys/vm/hugetlb_pool. This statistic only appears on the x86, Itanium, and AMD64 architectures.
HugePages_Free — The total number of hugepages available for the system. This statistic only appears on the x86, Itanium, and AMD64 architectures.
HugePages_Rsvd — The number of unused huge pages reserved for hugetlbfs.
HugePages_Surp — The number of surplus huge pages.
Hugepagesize — The size for each hugepages unit in kibibytes. By default, the value is 4096 KB on uniprocessor kernels for 32 bit architectures. For SMP, hugemem kernels, and AMD64, the default is 2048 KB. For Itanium architectures, the default is 262144 KB. This statistic only appears on the x86, Itanium, and AMD64 architectures.
DirectMap4k — The amount of memory, in kibibytes, mapped into kernel address space with 4 kB page mappings.
DirectMap2M — The amount of memory, in kibibytes, mapped into kernel address space with 2 MB page mappings.
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