From mboxrd@z Thu Jan 1 00:00:00 1970 From: Jiang Liu Date: Thu, 20 Aug 2015 06:36:12 +0000 Subject: Re: [Patch V3 3/9] sgi-xp: Replace cpu_to_node() with cpu_to_mem() to support memoryless node Message-Id: <55D5755C.5060803@linux.intel.com> List-Id: References: <1439781546-7217-1-git-send-email-jiang.liu@linux.intel.com> <1439781546-7217-4-git-send-email-jiang.liu@linux.intel.com> <55D43C63.7060802@linux.intel.com> In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: David Rientjes Cc: Andrew Morton , Mel Gorman , Mike Galbraith , Peter Zijlstra , "Rafael J . Wysocki" , Tang Chen , Tejun Heo , Cliff Whickman , Robin Holt , Tony Luck , linux-mm@kvack.org, linux-hotplug@vger.kernel.org, linux-kernel@vger.kernel.org, x86@kernel.org On 2015/8/20 8:02, David Rientjes wrote: > On Wed, 19 Aug 2015, Jiang Liu wrote: > >>> Why not simply fix build_zonelists_node() so that the __GFP_THISNODE >>> zonelists are set up to reference the zones of cpu_to_mem() for memoryless >>> nodes? >>> >>> It seems much better than checking and maintaining every __GFP_THISNODE >>> user to determine if they are using a memoryless node or not. I don't >>> feel that this solution is maintainable in the longterm. >> Hi David, >> There are some usage cases, such as memory migration, >> expect the page allocator rejecting memory allocation requests >> if there is no memory on local node. So we have: >> 1) alloc_pages_node(cpu_to_node(), __GFP_THISNODE) to only allocate >> memory from local node. >> 2) alloc_pages_node(cpu_to_mem(), __GFP_THISNODE) to allocate memory >> from local node or from nearest node if local node is memoryless. >> > > Right, so do you think it would be better to make the default zonelists be > setup so that cpu_to_node()->zonelists = cpu_to_mem()->zonelists and then > individual callers that want to fail for memoryless nodes check > populated_zone() themselves? Hi David, Great idea:) I think that means we are going to kill the concept of memoryless node, and we only need to specially handle a few callers who really care about whether there is memory on local node. Then I need some time to audit all usages of __GFP_THISNODE and update you whether it's doable. Thanks! Gerry