Re: [PATCH -mm 3/6] slub: introduce __kfree_rcu

["Paul E. McKenney" <paulmck@linux.vnet.ibm.com>]

On Thu, Mar 05, 2009 at 09:39:03AM -0500, Christoph Lameter wrote:
> On Thu, 5 Mar 2009, Lai Jiangshan wrote:
> 
> > The first parameter of __kfree_rcu() is unused in slab,slub,slqb.
> > (I used it before, for CONFIG_SLUB_DEBUG=y ...etc. But I found
> > these debugging code is needless)
> >
> > Object sizes of the memory objects in slob's kmalloc-slab are various.
> > We hardly calculate the start address of the object from the rcu address.
> 
> But you can start with the descriptor at the beginning of the page and
> scan until you find the object.

Another approach would be to keep a per-page bitmap of the objects
that are awaiting a grace period.

Not sure whether or not it is worthwhile, but it does reduce the
per-object overhead to two bits (one for the objects awaiting the
current grace period, the other for objects that will await the next
grace period).

							Thanx, Paul