system.mem Metrics from DataDog

Name

• system.mem.buffered

• MB (Uint)
• The amount of physical RAM used for file buffers.

• system.mem.cached

• MB (Uint)
• The amount of physical RAM used as cache memory.

• system.mem.free

• MB (Uint)
• The amount of free RAM.

• system.mem.page_tables

• MB (Uint)
• The amount of memory dedicated to the lowest page table level.

• system.mem.pct_usable

• fraction (Uint)
• The amount of usable physical RAM as a fraction of the total.

• system.mem.shared

• MB (Uint)
• The amount of physical RAM used as shared memory.

• system.mem.slab

• MB (Uint)
• The amount of memory used by the kernel to cache data structures for its own use.

• system.mem.total

• MB (Uint)
• The total amount of physical RAM.

• system.mem.usable

• MB (Uint)
• Value of MemAvailable from /proc/meminfo if present, but falls back to adding free + buffered + cached memory if not.

• system.mem.used

• MB (Uint)
• The amount of RAM in use.

• system.swap.cached

• MB (Uint)
• The amount of swap used as cache memory.

• system.swap.free

• MB (Uint)
• The amount of free swap space.

• system.swap.pct_free

• fraction (Uint)
• The amount of swap space not in use as a fraction of the total.

• system.swap.total

• MB (Uint)
• The total amount of swap space.

• system.swap.used

• MB (Uint)
• The amount of swap space in use.

计算公式：

system.mem.total = physTotal = MemTotal / 1024
system.mem.free = physFree = MemFree / 1024
system.mem.buffered = physBuffers = Buffers / 1024
system.mem.cached = physCached = Cached / 1024
system.mem.shared = physShared = Shmem / 1024
system.mem.slab = physSlab = Slab / 1024
system.mem.page_tables = physPageTables = PageTables / 1024
system.mem.used = physUsed = physTotal - physFree

if MemAvailable:
  physUsable = MemAvailable / 1024
else:
  physUsable = physFree + physBuffers + physCached
system.mem.usable = physUsable
system.mem.pct_usable = physPctUsable = physUsable / physTotal

system.swap.total = swapTotal = SwapTotal / 1024
system.swap.free = swapFree = SwapFree / 1024
system.swap.cached = swapCached = SwapCached / 1024
system.swap.used = swapUsed = swapTotal - swapFree
system.swap.pct_free = swapPctFree = swapFree / swapTotal

数据来源

针对Linux系统，内存相关Metrics来自/proc/meminfo文件。

/proc/meminfo文件内容示例

cat /proc/meminfo

MemTotal:       30716112 kB
MemFree:         1500476 kB
MemAvailable:    9589168 kB
Buffers:              84 kB
Cached:          8168688 kB
SwapCached:            0 kB
Active:         20373928 kB
Inactive:        3593908 kB
Active(anon):   17035548 kB
Inactive(anon):   590728 kB
Active(file):    3338380 kB
Inactive(file):  3003180 kB
Unevictable:           0 kB
Mlocked:               0 kB
SwapTotal:             0 kB
SwapFree:              0 kB
Dirty:              2160 kB
Writeback:             0 kB
AnonPages:      15798992 kB
Mapped:           630452 kB
Shmem:           1827160 kB
Slab:            4452204 kB
SReclaimable:    2138868 kB
SUnreclaim:      2313336 kB
KernelStack:       69808 kB
PageTables:       156740 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:    15358056 kB
Committed_AS:   36459124 kB
VmallocTotal:   34359738367 kB
VmallocUsed:      278560 kB
VmallocChunk:   34359278592 kB
HardwareCorrupted:     0 kB
AnonHugePages:   2367488 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       2048 kB
DirectMap4k:      342016 kB
DirectMap2M:    31115264 kB