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[37.188.168.3]) by smtp.gmail.com with ESMTPSA id f16sm9565775wmh.27.2020.06.24.13.07.51 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Wed, 24 Jun 2020 13:07:51 -0700 (PDT) Date: Wed, 24 Jun 2020 22:07:50 +0200 From: Michal Hocko To: Ben Widawsky Cc: linux-mm , Andi Kleen , Andrew Morton , Christoph Lameter , Dan Williams , Dave Hansen , David Hildenbrand , David Rientjes , Jason Gunthorpe , Johannes Weiner , Jonathan Corbet , Kuppuswamy Sathyanarayanan , Lee Schermerhorn , Li Xinhai , Mel Gorman , Mike Kravetz , Mina Almasry , Tejun Heo , Vlastimil Babka , linux-api@vger.kernel.org Subject: Re: [PATCH 00/18] multiple preferred nodes Message-ID: <20200624200750.GY1320@dhcp22.suse.cz> References: <20200619162425.1052382-1-ben.widawsky@intel.com> <20200622070957.GB31426@dhcp22.suse.cz> <20200623112048.GR31426@dhcp22.suse.cz> <20200623161211.qjup5km5eiisy5wy@intel.com> <20200624075216.GC1320@dhcp22.suse.cz> <20200624161643.75fkkvsxlmp3bf2e@intel.com> <20200624183917.GW1320@dhcp22.suse.cz> <20200624193733.tqeligjd3pdvrsmi@intel.com> <20200624195158.GX1320@dhcp22.suse.cz> <20200624200140.dypw6snshshzlbwa@intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20200624200140.dypw6snshshzlbwa@intel.com> Sender: linux-api-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-api@vger.kernel.org On Wed 24-06-20 13:01:40, Ben Widawsky wrote: > On 20-06-24 21:51:58, Michal Hocko wrote: > > On Wed 24-06-20 12:37:33, Ben Widawsky wrote: > > > On 20-06-24 20:39:17, Michal Hocko wrote: > > > > On Wed 24-06-20 09:16:43, Ben Widawsky wrote: [...] > > > > > > Or do I miss something that really requires more involved approach like > > > > > > building custom zonelists and other larger changes to the allocator? > > > > > > > > > > I think I'm missing how this allows selecting from multiple preferred nodes. In > > > > > this case when you try to get the page from the freelist, you'll get the > > > > > zonelist of the preferred node, and when you actually scan through on page > > > > > allocation, you have no way to filter out the non-preferred nodes. I think the > > > > > plumbing of multiple nodes has to go all the way through > > > > > __alloc_pages_nodemask(). But it's possible I've missed the point. > > > > > > > > policy_nodemask() will provide the nodemask which will be used as a > > > > filter on the policy_node. > > > > > > Ah, gotcha. Enabling independent masks seemed useful. Some bad decisions got me > > > to that point. UAPI cannot get independent masks, and callers of these functions > > > don't yet use them. > > > > > > So let me ask before I actually type it up and find it's much much simpler, is > > > there not some perceived benefit to having both masks being independent? > > > > I am not sure I follow. Which two masks do you have in mind? zonelist > > and user provided nodemask? > > Internally, a nodemask_t for preferred node, and a nodemask_t for bound nodes. Each mask is a local to its policy object. -- Michal Hocko SUSE Labs