From mboxrd@z Thu Jan 1 00:00:00 1970 From: Christoph Hellwig Date: Mon, 29 Apr 2019 20:09:57 +0000 Subject: Re: DISCONTIGMEM is deprecated Message-Id: <20190429200957.GB27158@infradead.org> List-Id: References: <20190419094335.GJ18914@techsingularity.net> <20190419140521.GI7751@bombadil.infradead.org> <0100016a461809ed-be5bd8fc-9925-424d-9624-4a325a7a8860-000000@email.amazonses.com> <25cabb7c-9602-2e09-2fe0-cad3e54595fa@linux.ee> <20190428081353.GB30901@infradead.org> <3908561D78D1C84285E8C5FCA982C28F7E9140BA@ORSMSX104.amr.corp.intel.com> In-Reply-To: <3908561D78D1C84285E8C5FCA982C28F7E9140BA@ORSMSX104.amr.corp.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: "Luck, Tony" Cc: Christoph Hellwig , Meelis Roos , Christopher Lameter , Mel Gorman , Andrew Morton , Mikulas Patocka , James Bottomley , "linux-parisc@vger.kernel.org" , "linux-mm@kvack.org" , Vlastimil Babka , LKML , "linux-arch@vger.kernel.org" , "Yu, Fenghua" , "linux-ia64@vger.kernel.org" On Mon, Apr 29, 2019 at 04:58:09PM +0000, Luck, Tony wrote: > > ia64 has a such a huge number of memory model choices. Maybe we > > need to cut it down to a small set that actually work. > > SGI systems had extremely discontiguous memory (they used some high > order physical address bits in the tens/hundreds of terabyte range for the > node number ... so there would be a few GBytes of actual memory then > a huge gap before the next node had a few more Gbytes). > > I don't know of anyone still booting upstream on an SN2, so if we start doing > serious hack and slash the chances are high that SN2 will be broken (if it isn't > already). When I wrote this, I thought of !NUMA: flat mem NUMA: sparsemem SN2: discontig based on Meelis report. But now that you mention it, I bet SN2 has already died slow death from bitrot. It is so different in places, and it doesn't seem like anyone care - if people want room sized SGI machines the Origin is much more sexy (hello Thomas!) :) So maybe it it time to mark SN2 broken and see if anyone screams? Without SN2 the whole machvec mess could basically go away - the only real difference between the remaining machvecs is which iommu if any we set up.