From mboxrd@z Thu Jan 1 00:00:00 1970 From: Zoltan Menyhart Date: Thu, 30 Nov 2006 10:47:09 +0000 Subject: Re: ia64 ORDERROUNDDOWN issue Message-Id: <456EB6AD.6000406@bull.net> List-Id: References: <456D9FD2.2070906@bull.net> In-Reply-To: <456D9FD2.2070906@bull.net> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org >> Do we need a "max_order" variable that could be adjusted to some lower >> value that MAX_ORDER if we find the memory topology doesn't fit inside >> the lines? > > (Your email talks about nodes, but I am asuming that we're actually dealing > with per-zone concepts here) ...and ... > But I wonder if a better approach would be to teach ia64 to just throw away > the last 1 .. MAX_ORDER-1 pages from the oddball zone? Assume we've got a machine with a memory configuration: Node 0: 0 ... 4 Gbyte - 1 Node 1: 4 Gbyte ... 16 Gbyte - 1 Assume MAX_ORDER is 8 Gbytes (a single binary, for all of our machines, for maintenance reasons). An allocation of 8 Gbytes should have its chance. Therefore the global MAX_ORDER should not be diminished dynamically. Surely we do not want to throw away 4 Gbytes of memory. The kernel should support that both of the nodes have starting address at 0. Therefore the "node_bootmem_map"-s of both of the nodes include the address range 0 ... 4 Gbyte in the example above. The "node_bootmem_map" of node 1 just happens to contain 0-s in the range of 0 ... 4 Gbyte. A not-in-use level of the buddy allocator (the 8 Gbyte level on node 0 in the example above) does not cost too much, I think there is no use to add complexity to the allocator code. Thanks, Zoltan Menyhart P.S. I guess it is not an ia64-only issue.