Messages in this thread | | | Date | Wed, 22 Mar 2006 15:06:52 +0900 | From | Yasunori Goto <> | Subject | Re: [PATCH: 002/017]Memory hotplug for new nodes v.4.(change name old add_memory() to arch_add_memory()) |
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> On Tue, 21 Mar 2006 17:08:18 -0800 > Dave Hansen <haveblue@us.ibm.com> wrote: > > If I missed it before, please refresh my memory. But, if we're > > providing arch_nid_probe(addr), then why don't we just call it inside of > > add_memory() on the start address, instead of in the generic code? > > > I think just *probe* needs it. The firmware which supports memory-hotplug, ACPI, > i386/x86_64/ia64, can tell node number as pxm.(proximity domain) > > add_memory() can pass address of paddr as args, but can't pass *pxm*. > > We already maintain pxm <-> nid map. But paddr <-> nid map isn't now. > If add_memory() doesn't has nid as args, we have to maintain > (1) pxm <-> nid map. > (2) paddr <-> nid map. > Becasue pfn_to_nid() is maintained by SPARSEMEM itself now, *new* paddr<->nid map > is redundant, I think. And I think the firmware already has the map before calling > add_memory().
In ACPI's case, kernel has to do 3 steps to get node id from physicall address. 1) parse DSDT to get device handle of ACPI for new memory. This step can be described 3 detail steps. 1-1) search memory device in DSDT. 1-2) get _CRS of its memory device to see physicall address. 1-3) compare 1-2)'s address with required paddr. (its memory device might be for other memory.) If it is for new memory, then goto step 2), else goto 1-1) again. 2) get pxm against its device handle. It is just calling acpi_get_pxm(). 3) get node from pxm. If pxm is new one, new node id is assigned.
Step 1) is a bit complicated. But, when notify of memory hot-add event reaches via ACPI, its handle is already obtained. So, step 2) and 3) are enough to get node id. If node id can be passed at add_memory(), that is all. If not, kernel losts memory device handle information or node id once at calling add_memory(), and search memory device handle again by step 1).
In addition, if paddr to node id translation is called in add_memory(), then its code for -each arch- will be like followings. This will be close from ugly "copy and paste" again....... :-( add_memory(paddr) { nid = paddr_to_node_id(paddr) if (!node_online(nid)) { pgdat = hotadd_new_pgdat(nid, start); if (!pgdat) return -ENOMEM; } :
Bye.
-- Yasunori Goto
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