Hi...
there
are codes like the following which I can not understand:
unsigned int objnr = obj_to_index(cachep, slabp, objp);
slab_bufctl(slabp)[objnr] = slabp->free;
slabp->free = objnr;
slabp->inuse--;
and slab_bufctl(slabp) is (kmem_bufctl_t *)(slabp + 1).
Since slabp is a pointer to struct slab, then what does slabp + 1 point to?
the next slab? what is the meaning of slab_bufctl(slabp)[objnr] ?
Interesting ... I read UTLK and here's my understanding. slabp+1 points
to the object descriptor array ( +1 here means an address right after
slab descriptor). On the freed object descriptor
(slab_bufctl(slabp)[objnr] ), it is assigned the number of last freed
object's descriptor. In the slab-> free itself, it will be assigned the
current freed object descriptor number.
So, in ASCII art, it's like below:
slabp-> free ====pointing to === > current freed object descriptor
====pointing to==> second to last freed object
That way, the last freed will be the first one used again when a similar
object is allocated. The ASCII art itself, as you can guess, depict a
linked list LIFO style.
I can give wrong impression here, so feel free to argue.
regards,
Mulyadi.
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