From 3e347261a80b57df792ab9464b5f0ed59add53a8 Mon Sep 17 00:00:00 2001 From: Bob Picco Date: Sat, 3 Sep 2005 15:54:28 -0700 Subject: [PATCH] sparsemem extreme implementation With cleanups from Dave Hansen SPARSEMEM_EXTREME makes mem_section a one dimensional array of pointers to mem_sections. This two level layout scheme is able to achieve smaller memory requirements for SPARSEMEM with the tradeoff of an additional shift and load when fetching the memory section. The current SPARSEMEM implementation is a one dimensional array of mem_sections which is the default SPARSEMEM configuration. The patch attempts isolates the implementation details of the physical layout of the sparsemem section array. SPARSEMEM_EXTREME requires bootmem to be functioning at the time of memory_present() calls. This is not always feasible, so architectures which do not need it may allocate everything statically by using SPARSEMEM_STATIC. Signed-off-by: Andy Whitcroft Signed-off-by: Bob Picco Signed-off-by: Dave Hansen Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/Kconfig | 19 ++++++++++++++++--- 1 file changed, 16 insertions(+), 3 deletions(-) (limited to 'mm/Kconfig') diff --git a/mm/Kconfig b/mm/Kconfig index fc644c5c065..4e9937ac352 100644 --- a/mm/Kconfig +++ b/mm/Kconfig @@ -90,11 +90,24 @@ config HAVE_MEMORY_PRESENT def_bool y depends on ARCH_HAVE_MEMORY_PRESENT || SPARSEMEM +# +# SPARSEMEM_EXTREME (which is the default) does some bootmem +# allocations when memory_present() is called. If this can not +# be done on your architecture, select this option. However, +# statically allocating the mem_section[] array can potentially +# consume vast quantities of .bss, so be careful. +# +# This option will also potentially produce smaller runtime code +# with gcc 3.4 and later. +# +config SPARSEMEM_STATIC + def_bool n + # # Architectecture platforms which require a two level mem_section in SPARSEMEM # must select this option. This is usually for architecture platforms with # an extremely sparse physical address space. # -config ARCH_SPARSEMEM_EXTREME - def_bool n - depends on SPARSEMEM && 64BIT +config SPARSEMEM_EXTREME + def_bool y + depends on SPARSEMEM && !SPARSEMEM_STATIC -- cgit v1.2.3