#include "threads/palloc.h"
#include <bitmap.h>
#include <debug.h>
+#include <inttypes.h>
#include <round.h>
#include <stddef.h>
#include <stdint.h>
/* A memory pool. */
struct pool
{
- struct lock lock; /* Mutual exclusion. */
- struct bitmap *used_map; /* Bitmap of free pages. */
- uint8_t *start, *end; /* Start and end of pool. */
+ size_t first_page; /* Page number of first page. */
+ size_t page_cnt; /* Number of pages. */
};
+/* Tracks pages in use, with a lock protecting it. */
+static struct bitmap *used_map;
+static struct lock used_map_lock;
+
/* Two pools: one for kernel data, one for user pages. */
-struct pool kernel_pool, user_pool;
+static struct pool kernel_pool, user_pool;
+
+/* Maximum number of pages to put in user pool. */
+size_t max_user_pages = SIZE_MAX;
-static void init_pool (struct pool *, void *start, void *end,
+static void init_pool (struct pool *pool, size_t first_page, size_t page_cnt,
const char *name);
static bool page_from_pool (const struct pool *, void *page);
void
palloc_init (void)
{
- /* End of the kernel as recorded by the linker.
- See kernel.lds.S. */
- extern char _end;
-
- /* Free memory. */
- uint8_t *free_start = pg_round_up (&_end);
- uint8_t *free_end = ptov (ram_pages * PGSIZE);
- size_t free_pages = (free_end - free_start) / PGSIZE;
- uint8_t *free_middle = free_start + free_pages / 2 * PGSIZE;
-
- /* Give half of memory to kernel, half to user. */
- init_pool (&kernel_pool, free_start, free_middle, "kernel pool");
- init_pool (&user_pool, free_middle, free_end, "user pool");
+ /* used_map from 1 MB as long as necessary. */
+ size_t bitmap_start = 1024;
+ size_t bitmap_pages = DIV_ROUND_UP (bitmap_needed_bytes (ram_pages), PGSIZE);
+
+ /* Free space from the bitmap to the end of RAM. */
+ size_t free_start = bitmap_start + bitmap_pages;
+ size_t free_pages = ram_pages - free_start;
+
+ /* Kernel and user get half of free space each.
+ User space can be limited by max_user_pages. */
+ size_t half_free = free_pages / 2;
+ size_t kernel_pages = half_free;
+ size_t user_pages = half_free < max_user_pages ? half_free : max_user_pages;
+
+ used_map = bitmap_create_preallocated (ram_pages,
+ ptov (bitmap_start * PGSIZE),
+ bitmap_pages * PGSIZE);
+ init_pool (&kernel_pool, free_start, kernel_pages, "kernel pool");
+ init_pool (&user_pool, free_start + kernel_pages, user_pages, "use pool");
+ lock_init (&used_map_lock, "used_map");
+}
+
+/* Initializes POOL to start (named NAME) at physical page number
+ FIRST_PAGE and continue for PAGE_CNT pages. */
+static void
+init_pool (struct pool *pool, size_t first_page, size_t page_cnt,
+ const char *name)
+{
+ printf ("%zu pages available in %s.\n", page_cnt, name);
+ pool->first_page = first_page;
+ pool->page_cnt = page_cnt;
}
/* Obtains and returns a group of PAGE_CNT contiguous free pages.
void *
palloc_get_multiple (enum palloc_flags flags, size_t page_cnt)
{
- struct pool *pool = flags & PAL_USER ? &user_pool : &kernel_pool;
+ struct pool *pool;
void *pages;
size_t page_idx;
if (page_cnt == 0)
return NULL;
- lock_acquire (&pool->lock);
+ pool = flags & PAL_USER ? &user_pool : &kernel_pool;
+
+ lock_acquire (&used_map_lock);
+ page_idx = bitmap_scan_and_flip (used_map,
+ pool->first_page, pool->page_cnt,
+ false);
+ lock_release (&used_map_lock);
- page_idx = bitmap_scan_and_flip (pool->used_map, 0, page_cnt, false);
if (page_idx != BITMAP_ERROR)
- pages = pool->start + PGSIZE * page_idx;
+ pages = ptov (PGSIZE * page_idx);
else
pages = NULL;
PANIC ("palloc_get: out of pages");
}
- lock_release (&pool->lock);
-
return pages;
}
else
NOT_REACHED ();
- page_idx = pg_no (pages) - pg_no (pool->start);
- ASSERT (pg_no (pages) + page_cnt <= pg_no (pool->end));
+ page_idx = vtop (pages) / PGSIZE;
#ifndef NDEBUG
memset (pages, 0xcc, PGSIZE * page_cnt);
#endif
- lock_acquire (&pool->lock);
- ASSERT (bitmap_all (pool->used_map, page_idx, page_idx + page_cnt));
- bitmap_set_multiple (pool->used_map, page_idx, page_idx + page_cnt, false);
- lock_release (&pool->lock);
+ ASSERT (bitmap_all (used_map, page_idx, page_cnt));
+ bitmap_set_multiple (used_map, page_idx, page_cnt, false);
}
/* Frees the page at PAGE. */
palloc_free_multiple (page, 1);
}
-/* Initializes pool P as starting at START and ending at END,
- naming it NAME for debugging purposes. */
-static void
-init_pool (struct pool *p, void *start, void *end, const char *name)
-{
- size_t bitmap_size;
- size_t page_cnt;
-
- ASSERT (pg_ofs (start) == 0);
- ASSERT (pg_ofs (end) == 0);
- ASSERT (end > start);
-
- page_cnt = pg_no (end) - pg_no (start);
- printf ("%d kB allocated for %s.\n", (PGSIZE / 1024) * page_cnt, name);
-
- lock_init (&p->lock, name);
- bitmap_size = ROUND_UP (bitmap_needed_bytes (page_cnt), PGSIZE);
- page_cnt -= bitmap_size / PGSIZE;
- p->used_map = bitmap_create_preallocated (page_cnt, start, bitmap_size);
- p->start = start + bitmap_size;
- p->end = end;
- ASSERT (p->end > p->start);
-}
-
/* Returns true if PAGE was allocated from POOL,
false otherwise. */
static bool
-page_from_pool (const struct pool *pool, void *page_)
+page_from_pool (const struct pool *pool, void *page)
{
- uint8_t *page = page_;
+ size_t phys_page_no = vtop (page) / PGSIZE;
- return page >= pool->start && page < pool->end;
+ return (phys_page_no >= pool->first_page
+ && phys_page_no < pool->first_page + pool->page_cnt);
}
projects / pintos-anon / blobdiff