Rewrite page allocator to support multi-page allocations.

[pintos-anon] / src / threads / malloc.c

diff --git a/src/threads/malloc.c b/src/threads/malloc.c
index 28f2324c79ef190d3357393546d80f5caff03546..487e93875ef4124ac314a7355429d4c2a632d1ab 100644 (file)
--- a/src/threads/malloc.c
+++ b/src/threads/malloc.c
@@ -1,11 +1,13 @@
-#include "malloc.h"
+#include "threads/malloc.h"
+#include <debug.h>
+#include <list.h>
+#include <round.h>

 #include <stdint.h>
 #include <stdint.h>

-#include "mmu.h"
-#include "palloc.h"
-#include "synch.h"
-#include "lib/debug.h"
-#include "lib/lib.h"
-#include "lib/list.h"
+#include <stdio.h>
+#include <string.h>
+#include "threads/mmu.h"
+#include "threads/palloc.h"
+#include "threads/synch.h"

 
 /* A simple implementation of malloc().
 
 
 /* A simple implementation of malloc().
 


@@ -26,10 +28,11 @@
    blocks, we remove all of the arena's blocks from the free list
    and give the arena back to the page allocator.
 
    blocks, we remove all of the arena's blocks from the free list
    and give the arena back to the page allocator.
 

-   Major limitation: the largest block that can be allocated is
-   PGSIZE / 2, or 2 kB.  Use palloc_get() to allocate pages (4 kB
-   blocks).  You're on your own if you need more memory than
-   that. */
+   We can't handle blocks bigger than 2 kB using this scheme,
+   because they're too big to fit in a single page with a
+   descriptor.  We handle those by allocating contiguous pages
+   with the page allocator and sticking the allocation size at
+   the beginning of the allocated block's arena header. */

 
 /* Descriptor. */
 struct desc
 
 /* Descriptor. */
 struct desc


@@ -40,11 +43,15 @@ struct desc
     struct lock lock;           /* Lock. */
   };
 
     struct lock lock;           /* Lock. */
   };
 

+/* Magic number for detecting arena corruption. */
+#define ARENA_MAGIC 0x9a548eed
+

 /* Arena. */
 struct arena 
   {
 /* Arena. */
 struct arena 
   {

-    struct desc *desc;          /* Owning descriptor. */
-    size_t free_cnt;            /* Number of free blocks. */
+    unsigned magic;             /* Always set to ARENA_MAGIC. */
+    struct desc *desc;          /* Owning descriptor, null for big block. */
+    size_t free_cnt;            /* Free blocks; pages in big block. */

   };
 
 /* Free block. */
   };
 
 /* Free block. */


@@ -54,7 +61,7 @@ struct block
   };
 
 /* Our set of descriptors. */
   };
 
 /* Our set of descriptors. */

-static struct desc descs[16];   /* Descriptors. */
+static struct desc descs[10];   /* Descriptors. */

 static size_t desc_cnt;         /* Number of descriptors. */
 
 static struct arena *block_to_arena (struct block *);
 static size_t desc_cnt;         /* Number of descriptors. */
 
 static struct arena *block_to_arena (struct block *);


@@ -66,7 +73,7 @@ malloc_init (void)
 {
   size_t block_size;
 
 {
   size_t block_size;
 

-  for (block_size = 16; block_size < PGSIZE; block_size *= 2)
+  for (block_size = 16; block_size < PGSIZE / 2; block_size *= 2)

     {
       struct desc *d = &descs[desc_cnt++];
       ASSERT (desc_cnt <= sizeof descs / sizeof *descs);
     {
       struct desc *d = &descs[desc_cnt++];
       ASSERT (desc_cnt <= sizeof descs / sizeof *descs);


@@ -93,12 +100,23 @@ malloc (size_t size)
   /* Find the smallest descriptor that satisfies a SIZE-byte
      request. */
   for (d = descs; d < descs + desc_cnt; d++)
   /* Find the smallest descriptor that satisfies a SIZE-byte
      request. */
   for (d = descs; d < descs + desc_cnt; d++)

-    if (size < d->block_size)
+    if (d->block_size >= size)

       break;
   if (d == descs + desc_cnt) 
     {
       break;
   if (d == descs + desc_cnt) 
     {

-      printk ("malloc: %zu byte allocation too big\n", size);
-      return NULL; 
+      /* SIZE is too big for any descriptor.
+         Allocate enough pages to hold SIZE plus an arena. */
+      size_t page_cnt = DIV_ROUND_UP (size + sizeof *a, PGSIZE);
+      a = palloc_get_multiple (0, page_cnt);
+      if (a == NULL)
+        return NULL;
+
+      /* Initialize the arena to indicate a big block of PAGE_CNT
+         pages, and return it. */
+      a->magic = ARENA_MAGIC;
+      a->desc = NULL;
+      a->free_cnt = page_cnt;
+      return a + 1;

     }
 
   lock_acquire (&d->lock);
     }
 
   lock_acquire (&d->lock);


@@ -109,7 +127,7 @@ malloc (size_t size)
       size_t i;
 
       /* Allocate a page. */
       size_t i;
 
       /* Allocate a page. */

-      a = palloc_get (0);
+      a = palloc_get_page (0);

       if (a == NULL) 
         {
           lock_release (&d->lock);
       if (a == NULL) 
         {
           lock_release (&d->lock);


@@ -117,11 +135,12 @@ malloc (size_t size)
         }
 
       /* Initialize arena and add its blocks to the free list. */
         }
 
       /* Initialize arena and add its blocks to the free list. */

+      a->magic = ARENA_MAGIC;

       a->desc = d;
       a->free_cnt = d->blocks_per_arena;
       for (i = 0; i < d->blocks_per_arena; i++) 
         {
       a->desc = d;
       a->free_cnt = d->blocks_per_arena;
       for (i = 0; i < d->blocks_per_arena; i++) 
         {

-          b = arena_to_block (a, i);
+          struct block *b = arena_to_block (a, i);

           list_push_back (&d->free_list, &b->free_elem);
         }
     }
           list_push_back (&d->free_list, &b->free_elem);
         }
     }


@@ -160,13 +179,28 @@ calloc (size_t a, size_t b)
 void
 free (void *p) 
 {
 void
 free (void *p) 
 {

-  struct block *b = p;
-  struct arena *a = block_to_arena (b);
-  struct desc *d = a->desc;
+  struct block *b;
+  struct arena *a;
+  struct desc *d;

 
   if (p == NULL)
     return;
 
 
   if (p == NULL)
     return;
 

+  b = p;
+  a = block_to_arena (b);
+  d = a->desc;
+
+  if (d == NULL) 
+    {
+      /* It's a big block.  Free its pages. */
+      palloc_free_multiple (a, a->free_cnt);
+      return;
+    }
+
+#ifndef NDEBUG
+  memset (b, 0xcd, d->block_size);
+#endif
+  

   lock_acquire (&d->lock);
 
   /* Add block to free list. */
   lock_acquire (&d->lock);
 
   /* Add block to free list. */


@@ -183,7 +217,7 @@ free (void *p)
           struct block *b = arena_to_block (a, i);
           list_remove (&b->free_elem);
         }
           struct block *b = arena_to_block (a, i);
           list_remove (&b->free_elem);
         }

-      palloc_free (a);
+      palloc_free_page (a);

     }
 
   lock_release (&d->lock);
     }
 
   lock_release (&d->lock);


@@ -193,13 +227,18 @@ free (void *p)
 static struct arena *
 block_to_arena (struct block *b)
 {
 static struct arena *
 block_to_arena (struct block *b)
 {

-  return pg_round_down (b);
+  struct arena *a = pg_round_down (b);
+  ASSERT (a != NULL);
+  ASSERT (a->magic == ARENA_MAGIC);
+  return a;

 }
 
 /* Returns the (IDX - 1)'th block within arena A. */
 static struct block *
 arena_to_block (struct arena *a, size_t idx) 
 {
 }
 
 /* Returns the (IDX - 1)'th block within arena A. */
 static struct block *
 arena_to_block (struct arena *a, size_t idx) 
 {

+  ASSERT (a != NULL);
+  ASSERT (a->magic == ARENA_MAGIC);

   ASSERT (idx < a->desc->blocks_per_arena);
   return (struct block *) ((uint8_t *) a
                            + sizeof *a
   ASSERT (idx < a->desc->blocks_per_arena);
   return (struct block *) ((uint8_t *) a
                            + sizeof *a