Messages in this thread Patch in this message | | | From | Michael Ellerman <> | Subject | Why no bigphysarea in mainline? | Date | Thu, 17 Mar 2005 20:57:04 +1100 |
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Hi all,
Can anyone recall if there's ever been a discussion about merging the bigphysarea patch (see below) into mainline? I couldn't find much of interest on google.
I realise bigphysarea is a bit of a hack, but it's no where near as big a hack as using mem=X to limit the kernel's memory and then using the rest of memory for your device driver.
The reason I'm curious is because I've gotten several queries about the mem=X option on PPC64 and whether it will support this hack, which it won't.
If no one has any fundamental objections I think it'd be good to get this merged into mainline so people start using it rather than mem=X hacks. To that end please let me know what you think is wrong with the patch as it stands (below).
cheers
Nick Martin's version for 2.6.9 (which applies to 2.6.11): http://www.ussg.iu.edu/hypermail/linux/kernel/0411.1/2076.html
And the guts of it:
Index: 2.6.11-bigphysarea/mm/bigphysarea.c =================================================================== --- /dev/null 1970-01-01 00:00:00.000000000 +0000 +++ 2.6.11-bigphysarea/mm/bigphysarea.c 2005-03-17 19:15:08.256421832 +1100 @@ -0,0 +1,353 @@ +/* linux/mm/bigphysarea.c, M. Welsh (mdw@xxxxxxxxxxxxxx) + * Copyright (c) 1996 by Matt Welsh. + * Extended by Roger Butenuth (butenuth@xxxxxxxxxxxxxxxx), October 1997 + * Extended for linux-2.1.121 till 2.4.0 (June 2000) + * by Pauline Middelink <middelink@xxxxxxxxxxx> + * Extended for linux-2.6.9 (November 2004) + * by Nick Martin <nim@xxxxxxx> + * + * This is a set of routines which allow you to reserve a large (?) + * amount of physical memory at boot-time, which can be allocated/deallocated + * by drivers. This memory is intended to be used for devices such as + * video framegrabbers which need a lot of physical RAM (above the amount + * allocated by kmalloc). This is by no means efficient or recommended; + * to be used only in extreme circumstances. + * + * This program is free software; you can redistribute it and/or modify + * it under the terms of the GNU General Public License as published by + * the Free Software Foundation; either version 2 of the License, or + * (at your option) any later version. + * + * This program is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU General Public License for more details. + * + * You should have received a copy of the GNU General Public License + * along with this program; if not, write to the Free Software + * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA. + * + */ + +#include <linux/config.h> +#include <linux/ptrace.h> +#include <linux/types.h> +#include <linux/kernel.h> +#include <linux/init.h> +#include <linux/pci.h> +#include <linux/proc_fs.h> +#include <linux/string.h> +#include <linux/mm.h> +#include <linux/bootmem.h> +#include <linux/errno.h> +#include <linux/bigphysarea.h> + +static int get_info(char* buf, char**, off_t, int); + +typedef struct range_struct { + struct range_struct *next; + caddr_t base; /* base of allocated block */ + size_t size; /* size in bytes */ +} range_t; + +/* + * 0: nothing initialized + * 1: bigphysarea_pages initialized + * 2: free list initialized + */ +static int init_level = 0; +static int bigphysarea_pages = 0; +static caddr_t bigphysarea = 0; +static range_t *free_list = NULL; +static range_t *used_list = NULL; +static struct resource mem_resource = { "Bigphysarea", 0, 0, IORESOURCE_MEM|IORESOURCE_BUSY }; + +static +int __init bigphysarea_init(void) +{ + if (bigphysarea_pages == 0 || bigphysarea == 0) + return -EINVAL; + + /* create to /proc entry for it */ + if (!create_proc_info_entry("bigphysarea",0444,NULL,get_info)) { + // ohoh, no way to free the allocated memory! + // continue without proc support, it not fatal in itself +// free_bootmem((unsigned long)bigphysarea>>PAGE_SHIFT,bigphysarea_pages<<PAGE_SHIFT); +// bigphysarea = 0; +// return -ENOMEM; + } + + init_level = 1; + + printk(KERN_INFO "bigphysarea: Allocated %d pages at 0x%p.\n", + bigphysarea_pages, bigphysarea); + + return 0; +} + +__initcall(bigphysarea_init); + +/* + * call when 'bigphysarea=' is given on the commandline. + * + * Strangely, bootmem is still active during this call, but + * during the processing of the initcalls it isn't anymore! + * So we alloc the needed memory here instead of bigphysarea_init(). + */ +static +int __init bigphysarea_setup(char *str) +{ + int par; + if (get_option(&str,&par)) { + bigphysarea_pages = par; + // Alloc the memory + bigphysarea = alloc_bootmem_low_pages(bigphysarea_pages<<PAGE_SHIFT); + if (!bigphysarea) { + printk(KERN_CRIT "bigphysarea: not enough memory for %d pages\n",bigphysarea_pages); + return -ENOMEM; + } + + // register the resource for it + mem_resource.start = bigphysarea; + mem_resource.end = mem_resource.start + (bigphysarea_pages<<PAGE_SHIFT); + request_resource(&iomem_resource, &mem_resource); + } + return 1; +} + +__setup("bigphysarea=", bigphysarea_setup); + +/* + * When we have pages but don't have a freelist, put all pages in + * one free list entry. Return 0 on success, 1 on error. + */ +static +int init2(int priority) +{ + if (init_level == 1) { + free_list = kmalloc(sizeof(range_t), priority); + if (free_list != NULL) { + free_list->next = NULL; + free_list->base = bigphysarea; + free_list->size = bigphysarea_pages * PAGE_SIZE; + init_level = 2; + return 0; + } + } + return 1; +} + + +/* + * Allocate `count' pages from the big physical area. Pages are aligned to + * a multiple of `align'. `priority' has the same meaning in kmalloc, it + * is needed for management information. + * This function may not be called from an interrupt! + */ +caddr_t bigphysarea_alloc_pages(int count, int align, int priority) +{ + range_t *range, **range_ptr, *new_range, *align_range; + caddr_t aligned_base; + + if (init_level < 2) + if (init2(priority)) + return 0; + new_range = NULL; + align_range = NULL; + + if (align == 0) + align = PAGE_SIZE; + else + align = align * PAGE_SIZE; + /* + * Search a free block which is large enough, even with alignment. + */ + range_ptr = &free_list; + while (*range_ptr != NULL) { + range = *range_ptr; + aligned_base = + (caddr_t)((((unsigned long)range->base + align - 1) / align) * align); + if (aligned_base + count * PAGE_SIZE <= + range->base + range->size) + break; + range_ptr = &range->next; + } + if (*range_ptr == NULL) + return 0; + range = *range_ptr; + /* + * When we have to align, the pages needed for alignment can + * be put back to the free pool. + * We check here if we need a second range data structure later + * and allocate it now, so that we don't have to check for a + * failed kmalloc later. + */ + if (aligned_base - range->base + count * PAGE_SIZE < range->size) { + new_range = kmalloc(sizeof(range_t), priority); + if (new_range == NULL) + return NULL; + } + if (aligned_base != range->base) { + align_range = kmalloc(sizeof(range_t), priority); + if (align_range == NULL) { + if (new_range != NULL) + kfree(new_range); + return NULL; + } + align_range->base = range->base; + align_range->size = aligned_base - range->base; + range->base = aligned_base; + range->size -= align_range->size; + align_range->next = range; + *range_ptr = align_range; + range_ptr = &align_range->next; + } + if (new_range != NULL) { + /* + * Range is larger than needed, create a new list element for + * the used list and shrink the element in the free list. + */ + new_range->base = range->base; + new_range->size = count * PAGE_SIZE; + range->base = new_range->base + new_range->size; + range->size = range->size - new_range->size; + } else { + /* + * Range fits perfectly, remove it from free list. + */ + *range_ptr = range->next; + new_range = range; + } + /* + * Insert block into used list + */ + new_range->next = used_list; + used_list = new_range; + + return new_range->base; +} +EXPORT_SYMBOL(bigphysarea_alloc_pages); + +/* + * Free pages allocated with `bigphysarea_alloc_pages'. `base' must be an + * address returned by `bigphysarea_alloc_pages'. + * This function my not be called from an interrupt! + */ +void bigphysarea_free_pages(caddr_t base) +{ + range_t *prev, *next, *range, **range_ptr; + + /* + * Search the block in the used list. + */ + for (range_ptr = &used_list; + *range_ptr != NULL; + range_ptr = &(*range_ptr)->next) + if ((*range_ptr)->base == base) + break; + if (*range_ptr == NULL) { + printk("bigphysarea_free_pages(0x%08x), not allocated!\n", + (unsigned)base); + return; + } + range = *range_ptr; + /* + * Remove range from the used list: + */ + *range_ptr = (*range_ptr)->next; + /* + * The free-list is sorted by address, search insertion point + * and insert block in free list. + */ + for (range_ptr = &free_list, prev = NULL; + *range_ptr != NULL; + prev = *range_ptr, range_ptr = &(*range_ptr)->next) + if ((*range_ptr)->base >= base) + break; + range->next = *range_ptr; + *range_ptr = range; + /* + * Concatenate free range with neighbors, if possible. + * Try for upper neighbor (next in list) first, then + * for lower neighbor (predecessor in list). + */ + if (range->next != NULL && + range->base + range->size == range->next->base) { + next = range->next; + range->size += range->next->size; + range->next = next->next; + kfree(next); + } + if (prev != NULL && + prev->base + prev->size == range->base) { + prev->size += prev->next->size; + prev->next = range->next; + kfree(range); + } +} +EXPORT_SYMBOL(bigphysarea_free_pages); + +caddr_t bigphysarea_alloc(int size) +{ + int pages = (size + PAGE_SIZE - 1) / PAGE_SIZE; + + return bigphysarea_alloc_pages(pages, 1, GFP_KERNEL); +} +EXPORT_SYMBOL(bigphysarea_alloc); + + +void bigphysarea_free(caddr_t addr, int size) +{ + (void)size; + bigphysarea_free_pages(addr); +} +EXPORT_SYMBOL(bigphysarea_free); + +static +int get_info(char *buf, char **a, off_t b, int c) +{ + char *p = buf; + range_t *ptr; + int free_count, free_total, free_max; + int used_count, used_total, used_max; + + if (init_level == 1) + init2(GFP_KERNEL); + + free_count = 0; + free_total = 0; + free_max = 0; + for (ptr = free_list; ptr != NULL; ptr = ptr->next) { + free_count++; + free_total += ptr->size; + if (ptr->size > free_max) + free_max = ptr->size; + } + + used_count = 0; + used_total = 0; + used_max = 0; + for (ptr = used_list; ptr != NULL; ptr = ptr->next) { + used_count++; + used_total += ptr->size; + if (ptr->size > used_max) + used_max = ptr->size; + } + + if (bigphysarea_pages == 0) { + p += sprintf(p, "No big physical area allocated!\n"); + return p - buf; + } + + p += sprintf(p, "Big physical area, size %ld kB\n", + bigphysarea_pages * PAGE_SIZE / 1024); + p += sprintf(p, " free list: used list:\n"); + p += sprintf(p, "number of blocks: %8d %8d\n", + free_count, used_count); + p += sprintf(p, "size of largest block: %8d kB %8d kB\n", + free_max / 1024, used_max / 1024); + p += sprintf(p, "total: %8d kB %8d kB\n", + free_total / 1024, used_total /1024); + + return p - buf; +}[unhandled content-type:application/pgp-signature] | |