On Wed, May 09, 2007 at 12:02:29PM +1000, Nick Piggin wrote: > BTW, we _really_ should be doing RCU properly in slob, because you > technically can't noop RCU on UP (even though the current users may be > safe...).
Thanks. Hugh was pretty convinced it was unneeded: http://marc.info/?l=linux-mm&m=116413907023393&w=2 And since I didn't care much about the SMP case, I didn't pursue it. This almost looks reasonable. I think HW_ALIGN | RCU is going to make it break though: > + if (unlikely(c->flags & SLAB_DESTROY_BY_RCU)) > + b += sizeof(struct slob_rcu); > + That could be dealt with by putting the slob_rcu at the end of the object and having the RCU helper function use ->size to work backward to the actual pointer. > void kmem_cache_free(struct kmem_cache *c, void *b) > { > if (c->dtor) > c->dtor(b, c, 0); I think if we want RCU to actually work, we want to run ->dtor in __kmem_cache_free? > - if (c->size < PAGE_SIZE) > - slob_free(b, c->size); > - else > - free_pages((unsigned long)b, find_order(c->size)); > + if (unlikely(c->flags & SLAB_DESTROY_BY_RCU)) { > + struct slob_rcu *slob_rcu; > + b -= sizeof(struct slob_rcu); > + slob_rcu = b; > + slob_rcu->size = c->size; Which means just store c in the header^Wfooter, then we can retrieve the size and the dtor in the RCU helper. We might as well add slab_is_available and make the damn thing work on sparsemem again too. -- Mathematics is the supreme nostalgia of our time. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
