Messages in this thread | | | Date | Tue, 8 May 2007 21:56:35 -0500 | From | Matt Mackall <> | Subject | Re: + fix-spellings-of-slab-allocator-section-in-init-kconfig.patch added to -mm tree |
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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.
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