I have a system with 1 GB of physical RAM. Right now, free shows the following memory usage:             total       used       free     shared    buffers     cachedMem:       1026360     863660     162700          0          0      50216-/+ buffers/cache:     813444     212916Swap:      5242876     500648    4742228So except the block cache, 813 MB are used. /proc/meminfo (which I'll post at the bottom due to length) tells me that, of this, 283 MB are mapped into userland processes (AnonPages + Mapped), and that 127 MB are used by the kernel (Slab + KernelStack + PageTables).That still leaves ~400 MB unaccounted for, however. Are my conceptions of how the system uses memory somewhat correct? Is there a way to tell what half of my memory is used for?MemTotal:        1026360 kBMemFree:          193768 kBBuffers:               0 kBCached:            28932 kBSwapCached:       101208 kBActive:           178816 kBInactive:         182476 kBActive(anon):     167196 kBInactive(anon):   168184 kBActive(file):      11620 kBInactive(file):    14292 kBUnevictable:        9848 kBMlocked:            9848 kBSwapTotal:       5242876 kBSwapFree:        4739272 kBDirty:                24 kBWriteback:             0 kBAnonPages:        268280 kBMapped:            14832 kBShmem:               280 kBSlab:             111828 kBSReclaimable:      27432 kBSUnreclaim:        84396 kBKernelStack:        2280 kBPageTables:        13200 kBNFS_Unstable:          0 kBBounce:                0 kBWritebackTmp:          0 kBCommitLimit:     5756056 kBCommitted_AS:    1506036 kBVmallocTotal:   34359738367 kBVmallocUsed:      145004 kBVmallocChunk:   34359581976 kBHardwareCorrupted:     0 kBAnonHugePages:         0 kBHugePages_Total:       0HugePages_Free:        0HugePages_Rsvd:        0HugePages_Surp:        0Hugepagesize:       2048 kBDirectMap4k:       79808 kBDirectMap2M:      968704 kB
What does Linux spend memory on other than userland, caches and slab?
linux;memory