Re: SLUB

[Christoph Lameter <clameter@sgi.com>]

On Fri, 21 Dec 2007, Mark Seger wrote:

> Sorry for being confused, but I thought that a slab was made up of a number of
> objects and above you're saying slab_size is the size of single object.
> Furthermore, looking at /sys/slab/shmem_inode_cache I see:
> 
> object_size = 960
> objs_per_slab = 4
> 
> which implies a slab is made up more than one object, so which is it?  could
> it be a simple matter of clearer names?  I also see

Yes a slab holds "objs_per_slab" object/
> 
> slab_size = 968
> 
> which certainly supports your statement about this being the size of an object
> and it looks like there is 8 bytes of overhead.  finally, I also see
> 
> objects = 242
> 
> and objects * obj_per_slab = slabsize.  is that a coincidence?

This means that the slab contains 242 active objects. From the "slabs" 
field you can deduce how many objects the slab could hold:

slabs * objs_per_slab

If you subtract "objects" from this then you have the number of unused 
objects in the slabs.

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