patch-2.3.23 linux/mm/bootmem.c

• Lines: 237
• Date: Wed Oct 20 16:46:42 1999
• Orig file: v2.3.22/linux/mm/bootmem.c
• Orig date: Wed Dec 31 16:00:00 1969

diff -u --recursive --new-file v2.3.22/linux/mm/bootmem.c linux/mm/bootmem.c
@@ -0,0 +1,236 @@
+/*
+ *  linux/mm/initmem.c
+ *
+ *  Copyright (C) 1999 Ingo Molnar
+ *
+ *  simple boot-time physical memory area allocator and
+ *  free memory collector. It's used to deal with reserved
+ *  system memory and memory holes as well.
+ */
+
+#include <linux/config.h>
+#include <linux/mm.h>
+#include <linux/kernel_stat.h>
+#include <linux/swap.h>
+#include <linux/swapctl.h>
+#include <linux/interrupt.h>
+#include <linux/init.h>
+#include <linux/bootmem.h>
+#include <asm/dma.h>
+
+/*
+ * Pointer to a bitmap - the bits represent all physical memory pages
+ * from physical address 0 to physical address end_mem.
+ *
+ * Access to this subsystem has to be serialized externally. (this is
+ * true for the boot process anyway)
+ */
+unsigned long max_low_pfn;
+
+static void * bootmem_map = NULL;
+
+/*
+ * Called once to set up the allocator itself.
+ */
+unsigned long __init init_bootmem (unsigned long start, unsigned long pages)
+{
+	unsigned long mapsize = (pages+7)/8;
+
+	if (bootmem_map)
+		BUG();
+	bootmem_map = __va(start << PAGE_SHIFT);
+	max_low_pfn = pages;
+
+	/*
+	 * Initially all pages are reserved - setup_arch() has to
+	 * register free RAM areas explicitly.
+	 */
+	memset(bootmem_map, 0xff, mapsize);
+
+	return mapsize;
+}
+
+/*
+ * Marks a particular physical memory range as usable. Usable RAM
+ * might be used for boot-time allocations - or it might get added
+ * to the free page pool later on.
+ */
+void __init reserve_bootmem (unsigned long addr, unsigned long size)
+{
+	unsigned long i;
+	/*
+	 * round up, partially reserved pages are considered
+	 * fully reserved.
+	 */
+	unsigned long end = (addr + size + PAGE_SIZE-1)/PAGE_SIZE;
+
+	if (!bootmem_map) BUG();
+	if (!size) BUG();
+
+	if (end > max_low_pfn)
+		BUG();
+	for (i = addr/PAGE_SIZE; i < end; i++)
+		if (test_and_set_bit(i, bootmem_map))
+			BUG();
+}
+
+void __init free_bootmem (unsigned long addr, unsigned long size)
+{
+	unsigned long i;
+	/*
+	 * round down end of usable mem, partially free pages are
+	 * considered reserved.
+	 */
+	unsigned long end = (addr + size)/PAGE_SIZE;
+
+	if (!bootmem_map) BUG();
+	if (!size) BUG();
+
+	if (end > max_low_pfn)
+		BUG();
+	for (i = addr/PAGE_SIZE; i < end; i++) {
+		if (!test_and_clear_bit(i, bootmem_map))
+			BUG();
+	}
+}
+
+/*
+ * We 'merge' subsequent allocations to save space. We might 'lose'
+ * some fraction of a page if allocations cannot be satisfied due to
+ * size constraints on boxes where there is physical RAM space
+ * fragmentation - in these cases * (mostly large memory boxes) this
+ * is not a problem.
+ *
+ * On low memory boxes we get it right in 100% of the cases.
+ */
+static unsigned long last_pos = 0;
+static unsigned long last_offset = 0;
+
+/*
+ * alignment has to be a power of 2 value.
+ */
+void * __init __alloc_bootmem (unsigned long size, unsigned long align, unsigned long goal)
+{
+	int area = 0;
+	unsigned long i, start = 0, reserved;
+	void *ret;
+	unsigned long offset, remaining_size;
+	unsigned long areasize, preferred;
+
+	if (!bootmem_map) BUG();
+	if (!size) BUG();
+
+	/*
+	 * We try to allocate bootmem pages above 'goal'
+	 * first, then we try to allocate lower pages.
+	 */
+	if (goal) {
+		preferred = goal >> PAGE_SHIFT;
+		if (preferred >= max_low_pfn)
+			preferred = 0;
+	} else
+		preferred = 0;
+
+	areasize = (size+PAGE_SIZE-1)/PAGE_SIZE;
+
+restart_scan:
+	for (i = preferred; i < max_low_pfn; i++) {
+		reserved = test_bit(i, bootmem_map);
+		if (!reserved) {
+			if (!area) {
+				area = 1;
+				start = i;
+			}
+			if (i - start + 1 == areasize)
+				goto found;
+		} else {
+			area = 0;
+			start = -1;
+		}
+	}
+	if (preferred) {
+		preferred = 0;
+		goto restart_scan;
+	}
+	BUG();
+found:
+	if (start >= max_low_pfn)
+		BUG();
+
+	/*
+	 * Is the next page of the previous allocation-end the start
+	 * of this allocation's buffer? If yes then we can 'merge'
+	 * the previous partial page with this allocation.
+	 */
+	if (last_offset && (last_pos+1 == start)) {
+		offset = (last_offset+align-1) & ~(align-1);
+		if (offset > PAGE_SIZE)
+			BUG();
+		remaining_size = PAGE_SIZE-offset;
+		if (remaining_size > PAGE_SIZE)
+			BUG();
+		if (size < remaining_size) {
+			areasize = 0;
+			// last_pos unchanged
+			last_offset = offset+size;
+			ret = __va(last_pos*PAGE_SIZE + offset);
+		} else {
+			size -= remaining_size;
+			areasize = (size+PAGE_SIZE-1)/PAGE_SIZE;
+			ret = __va(last_pos*PAGE_SIZE + offset);
+			last_pos = start+areasize-1;
+			last_offset = size;
+		}
+ 		last_offset &= ~PAGE_MASK;
+	} else {
+		last_pos = start + areasize - 1;
+		last_offset = size & ~PAGE_MASK;
+		ret = __va(start * PAGE_SIZE);
+	}
+	/*
+	 * Reserve the area now:
+	 */
+	for (i = start; i < start+areasize; i++)
+		if (test_and_set_bit(i, bootmem_map))
+			BUG();
+
+	return ret;
+}
+
+unsigned long __init free_all_bootmem (void)
+{
+	struct page * page;
+	unsigned long i, count, total = 0;
+
+	if (!bootmem_map) BUG();
+
+	page = mem_map;
+	count = 0;
+	for (i = 0; i < max_low_pfn; i++, page++) {
+		if (!test_bit(i, bootmem_map)) {
+			count++;
+			ClearPageReserved(page);
+			set_page_count(page, 1);
+			if (i >= (__pa(MAX_DMA_ADDRESS) >> PAGE_SHIFT))
+				clear_bit(PG_DMA, &page->flags);
+			__free_page(page);
+		}
+	}
+	total += count;
+	/*
+	 * Now free the allocator bitmap itself, it's not
+	 * needed anymore:
+	 */
+	page = mem_map + MAP_NR(bootmem_map);
+	count = 0;
+	for (i = 0; i < (max_low_pfn/8 + PAGE_SIZE-1)/PAGE_SIZE; i++,page++) {
+		count++;
+		ClearPageReserved(page);
+		set_page_count(page, 1);
+		__free_page(page);
+	}
+	total += count;
+	bootmem_map = NULL;
+
+	return total;
+}