From mboxrd@z Thu Jan 1 00:00:00 1970 From: David Mosberger Date: Mon, 09 May 2005 13:31:45 +0000 Subject: Re: mem_map Message-Id: <17023.26177.377922.550436@napali.hpl.hp.com> List-Id: References: <851caabb05050607291364149a@mail.gmail.com> In-Reply-To: <851caabb05050607291364149a@mail.gmail.com> MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit To: linux-ia64@vger.kernel.org >>>>> On Fri, 6 May 2005 19:59:59 +0530, Vaibhav Sharma said: Vaibhav> hi all, Can any body provide any information for the Vaibhav> significance of "CONFIG_VIRTUAL_MEM_MAP"? Turning on this option puts the Linux physical memory-map (mem_map) into virtual memory rather than physical memory. Doing so can be an advantage on machines which have holes in the physical memory. For example, on zx1-based machines, physical memory 1GB-4GB shows up at an address above 257GB so there is a hole of about 256GB below that address. There are other ways to manage (huge) holes in physical memory space, but with the large page-sizes (64MB or 16MB) we use on ia64 for identity-mapping kernel space, this approach seems to work quite well. --david