Why half of slabs are not shown in /proc/slabinfo?

[Andrey Borzenkov]

Mandriva kernel 2.6.30 using SLUB:

{pts/1}% grep SLUB /boot/config
CONFIG_SLUB_DEBUG=y
CONFIG_SLUB=y
# CONFIG_SLUB_DEBUG_ON is not set
# CONFIG_SLUB_STATS is not set

Some of slabs (e.g. filp) are not shown in /proc/slabinfo; comparing 
number of entries under /sys and slabinfo results in

{pts/0}% =ls -1 /sys/kernel/slab | grep -v : | wc -l
131
{pts/0}% wc -l /proc/slabinfo
68 /proc/slabinfo
{pts/0}%

so almost half of the all entries are missing. Is it expected or there 
is something wrong here?

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