e12401222f
This patch adds support for 256KB pages on ppc44x-based boards. For simplification of implementation with 256KB pages we still assume 2-level paging. As a side effect this leads to wasting extra memory space reserved for PTE tables: only 1/4 of pages allocated for PTEs are actually used. But this may be an acceptable trade-off to achieve the high performance we have with big PAGE_SIZEs in some applications (e.g. RAID). Also with 256KB PAGE_SIZE we increase THREAD_SIZE up to 32KB to minimize the risk of stack overflows in the cases of on-stack arrays, which size depends on the page size (e.g. multipage BIOs, NTFS, etc.). With 256KB PAGE_SIZE we need to decrease the PKMAP_ORDER at least down to 9, otherwise all high memory (2 ^ 10 * PAGE_SIZE == 256MB) we'll be occupied by PKMAP addresses leaving no place for vmalloc. We do not separate PKMAP_ORDER for 256K from 16K/64K PAGE_SIZE here; actually that value of 10 in support for 16K/64K had been selected rather intuitively. Thus now for all cases of PAGE_SIZE on ppc44x (including the default, 4KB, one) we have 512 pages for PKMAP. Because ELF standard supports only page sizes up to 64K, then you should use binutils later than 2.17.50.0.3 with '-zmax-page-size' set to 256K for building applications, which are to be run with the 256KB-page sized kernel. If using the older binutils, then you should patch them like follows: --- binutils/bfd/elf32-ppc.c.orig +++ binutils/bfd/elf32-ppc.c -#define ELF_MAXPAGESIZE 0x10000 +#define ELF_MAXPAGESIZE 0x40000 One more restriction we currently have with 256KB page sizes is inability to use shmem safely, so, for now, the 256KB is available only if you turn the CONFIG_SHMEM option off (another variant is to use BROKEN). Though, if you need shmem with 256KB pages, you can always remove the !SHMEM dependency in 'config PPC_256K_PAGES', and use the workaround available here: http://lkml.org/lkml/2008/12/19/20 Signed-off-by: Yuri Tikhonov <yur@emcraft.com> Signed-off-by: Ilya Yanok <yanok@emcraft.com> Signed-off-by: Josh Boyer <jwboyer@linux.vnet.ibm.com>
52 lines
1.3 KiB
C
52 lines
1.3 KiB
C
#ifndef _ASM_POWERPC_PAGE_32_H
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#define _ASM_POWERPC_PAGE_32_H
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#if defined(CONFIG_PHYSICAL_ALIGN) && (CONFIG_PHYSICAL_START != 0)
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#if (CONFIG_PHYSICAL_START % CONFIG_PHYSICAL_ALIGN) != 0
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#error "CONFIG_PHYSICAL_START must be a multiple of CONFIG_PHYSICAL_ALIGN"
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#endif
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#endif
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#define VM_DATA_DEFAULT_FLAGS VM_DATA_DEFAULT_FLAGS32
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#ifdef CONFIG_NOT_COHERENT_CACHE
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#define ARCH_KMALLOC_MINALIGN L1_CACHE_BYTES
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#endif
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#ifdef CONFIG_PTE_64BIT
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#define PTE_FLAGS_OFFSET 4 /* offset of PTE flags, in bytes */
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#else
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#define PTE_FLAGS_OFFSET 0
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#endif
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#ifdef CONFIG_PPC_256K_PAGES
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#define PTE_SHIFT (PAGE_SHIFT - PTE_T_LOG2 - 2) /* 1/4 of a page */
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#else
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#define PTE_SHIFT (PAGE_SHIFT - PTE_T_LOG2) /* full page */
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#endif
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#ifndef __ASSEMBLY__
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/*
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* The basic type of a PTE - 64 bits for those CPUs with > 32 bit
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* physical addressing.
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*/
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#ifdef CONFIG_PTE_64BIT
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typedef unsigned long long pte_basic_t;
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#else
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typedef unsigned long pte_basic_t;
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#endif
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struct page;
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extern void clear_pages(void *page, int order);
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static inline void clear_page(void *page) { clear_pages(page, 0); }
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extern void copy_page(void *to, void *from);
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#include <asm-generic/page.h>
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#define PGD_T_LOG2 (__builtin_ffs(sizeof(pgd_t)) - 1)
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#define PTE_T_LOG2 (__builtin_ffs(sizeof(pte_t)) - 1)
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#endif /* __ASSEMBLY__ */
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#endif /* _ASM_POWERPC_PAGE_32_H */
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