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Date:      Sun, 21 Jan 2018 22:15:23 +0100
From:      =?UTF-8?Q?Karsten_K=c3=b6nig?= <mail@kkoenig.net>
To:        freebsd-questions@freebsd.org
Subject:   Question about 'anonymous' UMA zones
Message-ID:  <8153a344-bd74-620c-3e05-47a28852beb6@kkoenig.net>

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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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