Question about 'anonymous' UMA zones
Karsten König
mail at kkoenig.net
Sun Jan 21 21:22:08 UTC 2018
Hello y'all,
I just played a little bit with the zone allocator of the FreeBSD kernel
and observed the following: All 'anonymous' zones (is this the
appropriate term?) with a size smaller than 512 Bytes have no slabs:
# vmstat -z
ITEM SIZE LIMIT USED FREE REQ FAIL SLEEP
...
16: 16, 0, 0, 0, 0, 0, 0
32: 32, 0, 0, 0, 0, 0, 0
64: 64, 0, 0, 0, 0, 0, 0
128: 128, 0, 0, 0, 0, 0, 0
256: 256, 0, 0, 0, 0, 0, 0
512: 512, 0, 7906, 70, 97681, 0, 0
...
I would like to know why this is the case; can someone explain this to
me? What happens if I allocate e.g. a 256 Byte buffer?
Best,
Karsten
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