slab usage in linux

Mulyadi Santosa mulyadi.santosa at
Tue Jan 4 11:29:44 EST 2011


I cc: the reply to the new list address. I hope you don't mind....
Now, let's what I can share here....

On Tue, Jan 4, 2011 at 18:49, Sowmya Sridharan <sowmya.sridharan at> wrote:
> I have seen slab cache increase by even 1GB, over two to three days on a
> stable system.(The system was sending and receiving bulk amounts of
> packets).

No kidding? 1 Gig? Wow.... But that's alright, I think that still make
sense ... highly frequent sock related cache creation I guess....
"slabtop -s c" would tell you the highest cache size ...

> When is slab usually freed?

AFAIK when it can no longer "grow".... same like page cache, it will
grow to fill your RAM  until  it exhausts everything left by anonymous
page allocation plus some amount of  reserved pages. And AFAIK too,
it's tunable, but I couldn't recall which kernel parameters that
control it.

>Also when I analyzed /proc/slabinfo, I was able
> to see that the number of active slab objects were increasing mostly for
> task_struct, dentry_cache and proc_inode_caches. When are these caches
> allotted objects, in general?

task_struct--> during new process creation

dentry_cache --> after reading directory entry metadata from a block
devices and cache them

proc_inode_cache --> almost similar like above, but this one is
strictly for /proc entries.


Mulyadi Santosa
Freelance Linux trainer and consultant


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