shrink address space reserved for kmap
PATCH 1/1 shrink address space reserved for kmap
If highmem is enabled, 32 MB at the top of the address space is reserved for kmap. This is not necessary: the kmap area is at most 4 MB long, reserving 8 MB is sufficient (the last few kB are needed for the fixmaps, and the kmap area must be 4 MB-aligned). Recovering these 24 MB is important - it's increases the size of the vmalloc pool. 2.6 contains a similar patch.
The patch also adds a safety check to detect a collision between fixmap and kmap mappings - just in case someone uses huge fixmaps.
Marcelo, could you add it to your tree?
--
Manfred
// $Header$
// Kernel Version:
// VERSION = 2 // PATCHLEVEL = 4 // SUBLEVEL = 21 // EXTRAVERSION = -pre2
include/asm-i386/highmem.h +1 -1
@@ -46,7 +46,7 @@* easily, subsequent pte tables have to be allocated in one physical * chunk of RAM. */ -#define PKMAP_BASE (0xfe000000UL) +#define PKMAP_BASE (0xff800000UL)#ifdef CONFIG_X86_PAE #define LAST_PKMAP 512#else
arch/i386/mm/init.c +9 -1
@@ -510,7 +510,15 @@if (!mem_map)BUG (); - +#ifdef CONFIG_HIGHMEM +/* check that fixmap and pkmap do not overlap */ +if (PKMAP_BASE +LAST_PKMAP *PAGE_SIZE >=FIXADDR_START ) { +printk (KERN_ERR "fixmap and kmap areas overlap - this will crash\n" ); +printk (KERN_ERR "pkstart: %lxh pkend: %lxh fixstart %lxh\n" , +PKMAP_BASE ,PKMAP_BASE +LAST_PKMAP *PAGE_SIZE ,FIXADDR_START ); +BUG (); + } +#endif set_max_mapnr_init (); high_memory = (void *)__va (max_low_pfn *PAGE_SIZE );