Messages in this thread | | | Date | Sat, 13 Oct 2007 14:00:25 +0900 | From | Yasunori Goto <> | Subject | Re: [Patch 002/002] Create/delete kmem_cache_node for SLUB on memory online callback |
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> On Fri, 12 Oct 2007, Yasunori Goto wrote: > > > > > + down_read(&slub_lock); > > > > + list_for_each_entry(s, &slab_caches, list) { > > > > + local_node = page_to_nid(virt_to_page(s)); > > > > + if (local_node == offline_node) > > > > + /* This slub is on the offline node. */ > > > > + return -EBUSY; > > > > + } > > > > + up_read(&slub_lock); > > > > > > So this checks if the any kmem_cache structure is on the offlined node? If > > > so then we cannot offline the node? > > > > Right. If slabs' migration is possible, here would be good place for > > doing it. But, it is not possible (at least now). > > I think you can avoid this check. The kmem_cache structures are allocated > from the kmalloc array. The check if the kmalloc slabs are empty will fail > if kmem_cache structures still exist on the node.
Ah, Ok.
> > > > > + * because the node is used by slub yet. > > > > + */ > > > > > > It may be clearer to say: > > > > > > "If nr_slabs > 0 then slabs still exist on the node that is going down. > > > We were unable to free them so we must fail." > > > > Again. If nr_slabs > 0, offline_pages must be fail due to slabs > > remaining on the node before. So, this callback isn't called. > > Ok then we can remove these checks?
Hmm. Yes. I'll remove it.
> > > > > +static int slab_mem_going_online_callback(void *arg) > > > > +{ > > > > + struct kmem_cache_node *n; > > > > + struct kmem_cache *s; > > > > + struct memory_notify *marg = arg; > > > > + int nid = marg->status_change_nid; > > > > + > > > > + /* If the node already has memory, then nothing is necessary. */ > > > > + if (nid < 0) > > > > + return 0; > > > > > > The node must have memory???? Or we have already brought up the code? > > > > kmem_cache_node is created at boot time if the node has memory. > > (Or, it is created by this callback on first added memory on the node). > > > > When nid = - 1, kmem_cache_node is created before this node due to > > node has memory. > > So the function can be called for a node that is already online?
already "node memory available", accurately ;-)
> > > > > + * New memory will be onlined on the node which has no memory so far. > > > > + * New kmem_cache_node is necssary for it. > > > > > > "We are bringing a node online. No memory is available yet. We must > > > allocate a kmem_cache_node structure in order to bring the node online." ? > > > > Your mention might be ok. > > But. I would like to prefer to define status of node hotplug for > > exactitude like followings > > > > > > A)Node online -- pgdat is created and can be accessed for this node. > > but there are no gurantee that cpu or memory is onlined. > > This status is very close from memory-less node. > > But this might be halfway status for node hotplug. > > Node online bit is set. But N_HIGH_MEMORY > > (or N_NORMAL_MEMORY) might be not set. > > Ahh.. Okay. > > > B)Node has memory-- > > one or more sections memory is onlined on the node. > > N_HIGH_MEMORY (or N_NORMAL_MEMORY) is set. > > > > If first memory is onlined on the node, the node status changes > > from A) to B). > > > > I feel this is very useful to manage "halfway status" of node > > hotplug. (So, memory-less node patch is very helpful for me.) > > > > So, I would like to avoid using the word "node online" at here. > > But, if above definition is messy for others, I'll change it. > > Ok can we talk about this as > > node online > > and > > node memory available?
Yes. Thanks.
-- Yasunori Goto
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