linux-kernel - 如何计算/proc/meminfo 中的 MemTotal

Question

当我 cat /proc/meminfo 时，报告如下:

MemTotal:        2034284 kB
MemFree:         1432728 kB
Buffers:           16568 kB
Cached:           324864 kB
SwapCached:            0 kB
Active:           307344 kB
Inactive:         256916 kB
Active(anon):     223020 kB
Inactive(anon):    74372 kB
Active(file):      84324 kB
Inactive(file):   182544 kB
Unevictable:           0 kB
Mlocked:               0 kB
HighTotal:       1152648 kB
HighFree:         600104 kB
LowTotal:         881636 kB
LowFree:          832624 kB
SwapTotal:       4200960 kB
SwapFree:        4200960 kB
Dirty:                60 kB
Writeback:             0 kB
AnonPages:        222868 kB
Mapped:            80596 kB
Shmem:             74564 kB
Slab:              24268 kB
SReclaimable:      14024 kB
SUnreclaim:        10244 kB
KernelStack:        1672 kB
PageTables:         2112 kB
NFS_Unstable:          0 kB
Bounce:                0 kB
WritebackTmp:          0 kB
CommitLimit:     5218100 kB
Committed_AS:     833352 kB
VmallocTotal:     122880 kB
VmallocUsed:       13916 kB
VmallocChunk:      50540 kB
HugePages_Total:       0
HugePages_Free:        0
HugePages_Rsvd:        0
HugePages_Surp:        0
Hugepagesize:       4096 kB
DirectMap4k:       20472 kB
DirectMap4M:      888832 kB

我得到了一个计算 Memtotal 的公式:

Memtotal = MemFree + Cached + Active + Inactive + Mapped + Shmem + Slab + PageTables + VmallocUsed

但我不知道公式是否正确，有人可以帮忙澄清一下吗？

Answer 1

我认为很难从 meminfo 获得确切的值(基于添加的总内存验证)。
尽管如此，我认为以下应该使您接近 TotalMemory 数字。

TotalMemory = MemFree + Buffers + Cached + Dirty + AnonPages + Slab + VmAllocUsed

在你的例子中
1432728 + 16568 + 324864 + 60 + 222868 + 24268 + 13916 = 2035272
一些引用:
http://git.kernel.org/cgit/linux/kernel/git/torvalds/linux.git/tree/Documentation/filesystems/proc.txt?id=HEAD#l451
(来自上面建议的另一篇stackoverflow文章)
除此之外，我认为波动是因为 VmAllocUsed。