x86_64 implement SPARSE_VIRTUAL x86_64 is using 2M page table entries to map its 1-1 kernel space. We implement the virtual memmap also using 2M page table entries. So there is no difference at all to FLATMEM. Both schemes require a page table and a TLB for each 2MB. FLATMEM still references memory since the mem_map pointer itself a variable. SPARSE_VIRTUAL uses a constant for vmemmap. Thus no memory reference. SPARSE_VIRTUAL should be superior to even FLATMEM. With this SPARSEMEM becomes the most efficient way of handling virt_to_page, pfn_to_page and friends for UP, SMP and NUMA on x86_64. Signed-off-by: Christoph Lameter <clameter@xxxxxxx> Index: linux-2.6.21-rc5-mm4/include/asm-x86_64/page.h =================================================================== --- linux-2.6.21-rc5-mm4.orig/include/asm-x86_64/page.h 2007-04-03 18:41:06.000000000 -0700 +++ linux-2.6.21-rc5-mm4/include/asm-x86_64/page.h 2007-04-03 18:41:59.000000000 -0700 @@ -128,6 +128,7 @@ extern unsigned long phys_base; VM_READ | VM_WRITE | VM_MAYREAD | VM_MAYWRITE | VM_MAYEXEC) #define __HAVE_ARCH_GATE_AREA 1 +#define vmemmap ((struct page *)0xffffe20000000000UL) #include <asm-generic/memory_model.h> #include <asm-generic/page.h> Index: linux-2.6.21-rc5-mm4/Documentation/x86_64/mm.txt =================================================================== --- linux-2.6.21-rc5-mm4.orig/Documentation/x86_64/mm.txt 2007-04-03 18:41:06.000000000 -0700 +++ linux-2.6.21-rc5-mm4/Documentation/x86_64/mm.txt 2007-04-03 18:41:59.000000000 -0700 @@ -9,6 +9,7 @@ ffff800000000000 - ffff80ffffffffff (=40 ffff810000000000 - ffffc0ffffffffff (=46 bits) direct mapping of all phys. memory ffffc10000000000 - ffffc1ffffffffff (=40 bits) hole ffffc20000000000 - ffffe1ffffffffff (=45 bits) vmalloc/ioremap space +ffffe20000000000 - ffffe2ffffffffff (=40 bits) virtual memory map ... unused hole ... ffffffff80000000 - ffffffff82800000 (=40 MB) kernel text mapping, from phys 0 ... unused hole ... Index: linux-2.6.21-rc5-mm4/arch/x86_64/Kconfig =================================================================== --- linux-2.6.21-rc5-mm4.orig/arch/x86_64/Kconfig 2007-04-03 18:41:06.000000000 -0700 +++ linux-2.6.21-rc5-mm4/arch/x86_64/Kconfig 2007-04-03 18:41:59.000000000 -0700 @@ -392,6 +392,12 @@ config ARCH_SPARSEMEM_ENABLE def_bool y depends on (NUMA || EXPERIMENTAL) +config SPARSE_VIRTUAL + def_bool y + +config ARCH_SUPPORTS_PMD_MAPPING + def_bool y + config ARCH_MEMORY_PROBE def_bool y depends on MEMORY_HOTPLUG - To unsubscribe from this list: send the line "unsubscribe linux-ia64" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
|