From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mel Gorman Subject: Re: DISCONTIGMEM is deprecated Date: Sun, 21 Apr 2019 22:16:04 +0100 Message-ID: <20190421211604.GN18914@techsingularity.net> References: <20190419094335.GJ18914@techsingularity.net> <20190419140521.GI7751@bombadil.infradead.org> <20190421063859.GA19926@rapoport-lnx> <20190421132606.GJ7751@bombadil.infradead.org> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Return-path: Content-Disposition: inline In-Reply-To: <20190421132606.GJ7751@bombadil.infradead.org> Sender: linux-kernel-owner@vger.kernel.org To: Matthew Wilcox Cc: Mike Rapoport , Andrew Morton , Mikulas Patocka , James Bottomley , linux-parisc@vger.kernel.org, linux-mm@kvack.org, Vlastimil Babka , LKML , linux-arch@vger.kernel.org List-Id: linux-arch.vger.kernel.org On Sun, Apr 21, 2019 at 06:26:07AM -0700, Matthew Wilcox wrote: > On Sun, Apr 21, 2019 at 09:38:59AM +0300, Mike Rapoport wrote: > > On Fri, Apr 19, 2019 at 07:05:21AM -0700, Matthew Wilcox wrote: > > > On Fri, Apr 19, 2019 at 10:43:35AM +0100, Mel Gorman wrote: > > > > DISCONTIG is essentially deprecated and even parisc plans to move to > > > > SPARSEMEM so there is no need to be fancy, this patch simply disables > > > > watermark boosting by default on DISCONTIGMEM. > > > > > > I don't think parisc is the only arch which uses DISCONTIGMEM for !NUMA > > > scenarios. Grepping the arch/ directories shows: > > > > > > alpha (does support NUMA, but also non-NUMA DISCONTIGMEM) > > > arc (for supporting more than 1GB of memory) > > > ia64 (looks complicated ...) > > > m68k (for multiple chunks of memory) > > > mips (does support NUMA but also non-NUMA) > > > parisc (both NUMA and non-NUMA) > > > > i386 NUMA as well > > I clearly over-trimmed. The original assumption that Mel had was that > DISCONTIGMEM => NUMA, and that's not true on the above six architectures. > It is true on i386 ;-) 32-bit NUMA systems should be non-existent in practice. The last NUMA system I'm aware of that was both NUMA and 32-bit only died somewhere between 2004 and 2007. If someone is running a 64-bit capable system in 32-bit mode with NUMA, they really are just punishing themselves for fun. -- Mel Gorman SUSE Labs From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Date: Sun, 21 Apr 2019 22:16:04 +0100 From: Mel Gorman Subject: Re: DISCONTIGMEM is deprecated Message-ID: <20190421211604.GN18914@techsingularity.net> References: <20190419094335.GJ18914@techsingularity.net> <20190419140521.GI7751@bombadil.infradead.org> <20190421063859.GA19926@rapoport-lnx> <20190421132606.GJ7751@bombadil.infradead.org> MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-15 Content-Disposition: inline In-Reply-To: <20190421132606.GJ7751@bombadil.infradead.org> To: Matthew Wilcox Cc: Mike Rapoport , Andrew Morton , Mikulas Patocka , James Bottomley , linux-parisc@vger.kernel.org, linux-mm@kvack.org, Vlastimil Babka , LKML , linux-arch@vger.kernel.org List-ID: Message-ID: <20190421211604.DJcTzmnm7qx3sWKAKb8VyLS5uSpXqi9x8KdbS_ZImYc@z> On Sun, Apr 21, 2019 at 06:26:07AM -0700, Matthew Wilcox wrote: > On Sun, Apr 21, 2019 at 09:38:59AM +0300, Mike Rapoport wrote: > > On Fri, Apr 19, 2019 at 07:05:21AM -0700, Matthew Wilcox wrote: > > > On Fri, Apr 19, 2019 at 10:43:35AM +0100, Mel Gorman wrote: > > > > DISCONTIG is essentially deprecated and even parisc plans to move to > > > > SPARSEMEM so there is no need to be fancy, this patch simply disables > > > > watermark boosting by default on DISCONTIGMEM. > > > > > > I don't think parisc is the only arch which uses DISCONTIGMEM for !NUMA > > > scenarios. Grepping the arch/ directories shows: > > > > > > alpha (does support NUMA, but also non-NUMA DISCONTIGMEM) > > > arc (for supporting more than 1GB of memory) > > > ia64 (looks complicated ...) > > > m68k (for multiple chunks of memory) > > > mips (does support NUMA but also non-NUMA) > > > parisc (both NUMA and non-NUMA) > > > > i386 NUMA as well > > I clearly over-trimmed. The original assumption that Mel had was that > DISCONTIGMEM => NUMA, and that's not true on the above six architectures. > It is true on i386 ;-) 32-bit NUMA systems should be non-existent in practice. The last NUMA system I'm aware of that was both NUMA and 32-bit only died somewhere between 2004 and 2007. If someone is running a 64-bit capable system in 32-bit mode with NUMA, they really are just punishing themselves for fun. -- Mel Gorman SUSE Labs