KernelStack Kernel stack size Mlocked Mlock()ed pages found and moved off LRU Unevictable Unevictable pages Shmem Shmem pages (included tmpfs/GEM pages) Inactive(anon) Inactive anonymous pages Active(file) Active file pages Active(anon) Active anonymous pages AnonHugePages Anonymous huge pages count Inactive(file) Inactive file pages DirectMap4k Directly mapped 4k pages DirectMap2M Directly mapped 2M pages HardwareCorrupted Number of pages corrupted by hardware failure Hugepagesize Size of one hugepage HugePages_Total The size of the pool of huge pages HugePages_Free The number of huge pages in the pool that are not yet allocated. HugePages_Rsvd Short for "reserved," and is the number of huge pages for which a commitment to allocate from the pool has been made, but no allocation has yet been made. Reserved huge pages guarantee that an application will be able to allocate a huge page from the pool of huge pages at fault time. HugePages_Surp is short for "surplus," and is the number of huge pages in the pool above the value in /proc/sys/vm/nr_hugepages. The maximum number of surplus huge pages is controlled by /proc/sys/vm/nr_overcommit_hugepages. MemTotal Total usable ram (i.e. physical ram minus a few reserved bits and the kernel binary code) MemFree The sum of LowFree+HighFree Buffers Relatively temporary storage for raw disk blocks shouldn't get tremendously large (20MB or so) Cached in-memory cache for files read from the disk (the pagecache). Doesn't include SwapCached SwapCached Memory that once was swapped out, is swapped back in but still also is in the swapfile (if memory is needed it doesn't need to be swapped out AGAIN because it is already in the swapfile. This saves I/O) Active Memory that has been used more recently and usually not reclaimed unless absolutely necessary. Inactive Memory which has been less recently used. It is more eligible to be reclaimed for other purposes HighTotal HighFree Highmem is all memory above ~860MB of physical memory Highmem areas are for use by userspace programs, or for the pagecache. The kernel must use tricks to access this memory, making it slower to access than lowmem. LowTotal LowFree Lowmem is memory which can be used for everything that highmem can be used for, but it is also available for the kernel's use for its own data structures. Among many other things, it is where everything from the Slab is allocated. Bad things happen when you're out of lowmem. SwapTotal total amount of swap space available SwapFree Memory which has been evicted from RAM, and is temporarily on the disk Dirty Memory which is waiting to get written back to the disk Writeback Memory which is actively being written back to the 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 SReclaimable Part of Slab, that might be reclaimed, such as caches SUnreclaim Part of Slab, that cannot be reclaimed on memory pressure PageTables amount of memory dedicated to the lowest level of page tables. NFS_Unstable NFS pages sent to the server, but not yet committed to stable storage Bounce Memory used for block device "bounce buffers" WritebackTmp Memory used by FUSE for temporary writeback 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. A process which malloc()'s 1G of memory, but only touches 300M of it will only show up as using 300M of memory even if it has the address space allocated for the entire 1G. This 1G is memory which has been "committed" to by the VM and can be used at any time by the allocating application. With strict overcommit enabled on the system (mode 2 in 'vm.overcommit_memory'), allocations which would exceed the CommitLimit (detailed above) will not be permitted. This is useful if one needs to guarantee that processes will not fail due to lack of memory once that memory has been successfully allocated. 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