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I couldn’t find any (recent) documentation on reading the output of the show-memory-usage SysRq (Alt+SysRq+m). So what can one learn from looking at it?

Here is an example output form my box (Kernel 3.9.5):

SysRq : Show Memory
Mem-Info:
DMA per-cpu:
CPU    0: hi:    0, btch:   1 usd:   0
CPU    1: hi:    0, btch:   1 usd:   0
DMA32 per-cpu:
CPU    0: hi:  186, btch:  31 usd:  13
CPU    1: hi:  186, btch:  31 usd:  46
active_anon:346766 inactive_anon:109 isolated_anon:0
active_file:1954 inactive_file:2465 isolated_file:0
unevictable:3794 dirty:8 writeback:0 unstable:0
free:6425 slab_reclaimable:2888 slab_unreclaimable:34070
mapped:3344 shmem:176 pagetables:67123 bounce:0
free_cma:0
DMA free:8916kB min:44kB low:52kB high:64kB active_anon:584kB inactive_anon:0kB active_file:144kB inactive_file:512kB unevictable:0kB isolated(anon):0kB isolated(file):0kB present:15988kB managed:15904kB mlocked:0kB dirty:0kB writeback:0kB mapped:180kB shmem:0kB slab_reclaimable:24kB slab_unreclaimable:5084kB kernel_stack:8kB pagetables:148kB unstable:0kB bounce:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no
lowmem_reserve[]: 0 1986 1986 1986
DMA32 free:16784kB min:5676kB low:7092kB high:8512kB active_anon:1386480kB inactive_anon:436kB active_file:7672kB inactive_file:9348kB unevictable:15176kB isolated(anon):0kB isolated(file):0kB present:2080320kB managed:2033884kB mlocked:15176kB dirty:32kB writeback:0kB mapped:13196kB shmem:704kB slab_reclaimable:11528kB slab_unreclaimable:131196kB kernel_stack:37960kB pagetables:268344kB unstable:0kB bounce:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no
lowmem_reserve[]: 0 0 0 0
DMA: 7*4kB (UM) 9*8kB (UM) 5*16kB (UM) 37*32kB (UEM) 16*64kB (UEM) 5*128kB (UEM) 7*256kB (M) 0*512kB 0*1024kB 0*2048kB 1*4096kB (R) = 8916kB
DMA32: 1124*4kB (EM) 500*8kB (UEMR) 64*16kB (UMR) 91*32kB (UEMR) 20*64kB (EMR) 16*128kB (UR) 4*256kB (UR) 0*512kB 0*1024kB 0*2048kB 0*4096kB = 16784kB
6062 total pagecache pages
0 pages in swap cache
Swap cache stats: add 0, delete 0, find 0/0
Free swap  = 0kB
Total swap = 0kB
524175 pages RAM
11057 pages reserved
1364519 pages shared
488355 pages non-shared

My laptop (with a more recent kernel) additionally reports information about some “normal” memory:

Normal per-cpu:
CPU    0: hi:  186, btch:  31 usd: 148
CPU    1: hi:  186, btch:  31 usd: 168

Normal free:471924kB min:33464kB low:41828kB high:50196kB active_anon:103096kB inactive_anon:34108kB active_file:155112kB inactive_file:165940kB unevictable:172kB isolated(anon):0kB isolated(file):0kB present:1048576kB managed:975852kB mlocked:172kB dirty:628kB writeback:0kB mapped:71088kB shmem:34284kB slab_reclaimable:20040kB slab_unreclaimable:6996kB kernel_stack:896kB pagetables:4728kB unstable:0kB bounce:0kB free_cma:0kB writeback_tmp:0kB pages_scanned:0 all_unreclaimable? no
lowmem_reserve[]: 0 0 0 0

Normal: 729*4kB (UEMR) 2317*8kB (UEMR) 4016*16kB (UEMR) 1699*32kB (UEMR) 654*64kB (UEMR) 374*128kB (UEMR) 250*256kB (UEMR) 152*512kB (UEMR) 96*1024kB (EMR) 1*2048kB (R) 0*4096kB = 471980kB

and has

0 pages HighMem/MovableOnly

instead of the last three lines.

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