Hugh Dickins [off-list ref] writes:

On Thu, 1 Jun 2017, Christoph Lameter wrote:

quoted

Ok so debugging was off but the slab cache has a ctor callback which
mandates that the free pointer cannot use the free object space when
the object is not in use. Thus the size of the object must be increased to
accomodate the freepointer.

Thanks a lot for working that out.  Makes sense, fully understood now,
nothing to worry about (though makes one wonder whether it's efficient
to use ctors on high-alignment caches; or whether an internal "zero-me"
ctor would be useful).

Or should we just be using kmem_cache_zalloc() when we allocate from
those slabs?

Given all the ctor's do is memset to 0.

cheers