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Date: Wed, 28 Oct 2009 09:31:38 +0100 From: Heiko Carstens <heiko.carstens@...ibm.com> To: David Rientjes <rientjes@...gle.com> Cc: Alex Chiang <achiang@...com>, Andrew Morton <akpm@...ux-foundation.org>, Gary Hade <garyhade@...ibm.com>, linux-kernel@...r.kernel.org, linux-mm@...ck.org, Badari Pulavarty <pbadari@...ibm.com>, Martin Schwidefsky <schwidefsky@...ibm.com>, Ingo Molnar <mingo@...e.hu> Subject: Re: [PATCH v2 1/5] mm: add numa node symlink for memory section in sysfs On Tue, Oct 27, 2009 at 02:27:56PM -0700, David Rientjes wrote: > On Tue, 27 Oct 2009, Alex Chiang wrote: > > > Thank you for ACKing, David. > > > > S390 guys, I cc'ed you on this patch because I heard a rumour > > that your memory sections may belong to more than one NUMA node? > > Is that true? If so, how would you like me to handle that > > situation? > > > > You're referring to how unregister_mem_sect_under_nodes() should be > handled, right? register_mem_sect_under_node() already looks supported by > your patch. > > Since the unregister function includes a plural "nodes," I assume that > it's possible for hotplug to register a memory section to more than one > node. That's probably lacking on x86 currently, however, because we lack > node hotplug. > > I'd suggest a similiar iteration through pfn's that the register function > does checking for multiple nodes and then removing the link from all > applicable node_devices kobj when unregistering. > > Maybe one of the s390 maintainers will test that? The short answer is: s390 doesn't support NUMA, because the hardware doesn't tell us to which node (book in s390 terms) a memory range belongs to. Memory layout for a logical partition is striped: first x mbyte belong to node 0, next x mbyte belong to node 1, etc... Also, since there is always a hypervisor running below Linux I don't think it would make too much sense if we would know to which node a piece of memory belongs to: if the hypervisor decides to schedule a virtual cpu of a logical partition to a different node then what? -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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