Question about 'anonymous' UMA zones

[Karsten Koenig]

Hello y'all,

it seems I could answer this myself. The root cause is that I compiled
my kernel with DEBUG_REDZONE for testing. I don't quite understand why
this happens for the lower zones, yet, but I guess I just have to read
the redzone code again.

Best,

Karsten

On 22.01.2018 13:00, freebsd-questions-request at freebsd.org wrote:
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