Use runtime options instead of conditional compilation for MLFQS,

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

diff --git a/src/threads/malloc.c b/src/threads/malloc.c
index 9910bf433c7b1f2eac0a518de062a9a00ed7cafc..f74d43960f60d11643728fd75b19c37d7c9ae354 100644 (file)
--- a/src/threads/malloc.c
+++ b/src/threads/malloc.c
@@ -1,6 +1,7 @@
 #include "threads/malloc.h"
 #include <debug.h>
 #include <list.h>
 #include "threads/malloc.h"
 #include <debug.h>
 #include <list.h>

+#include <round.h>

 #include <stdint.h>
 #include <stdio.h>
 #include <string.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <string.h>


@@ -27,10 +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


@@ -48,14 +50,14 @@ struct desc
 struct arena 
   {
     unsigned magic;             /* Always set to ARENA_MAGIC. */
 struct arena 
   {
     unsigned magic;             /* Always set to ARENA_MAGIC. */

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

   };
 
 /* Free block. */
 struct block 
   {
   };
 
 /* Free block. */
 struct block 
   {

-    list_elem free_elem;        /* Free list element. */
+    struct list_elem free_elem; /* Free list element. */

   };
 
 /* Our set of descriptors. */
   };
 
 /* Our set of descriptors. */


@@ -71,7 +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);


@@ -102,8 +104,19 @@ malloc (size_t size)
       break;
   if (d == descs + desc_cnt) 
     {
       break;
   if (d == descs + desc_cnt) 
     {

-      printf ("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);


@@ -114,7 +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);


@@ -148,7 +161,7 @@ calloc (size_t a, size_t b)
   void *p;
   size_t size;
 
   void *p;
   size_t size;
 

-  /* Calculate block size. */
+  /* Calculate block size and make sure it fits in size_t. */

   size = a * b;
   if (size < a || size < b)
     return NULL;
   size = a * b;
   if (size < a || size < b)
     return NULL;


@@ -177,13 +190,19 @@ free (void *p)
   a = block_to_arena (b);
   d = a->desc;
 
   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
 #ifndef NDEBUG

-  memset (b, 0xcd, d->block_size);
+  memset (b, 0xcc, d->block_size);

 #endif
   
   lock_acquire (&d->lock);
 
 #endif
   
   lock_acquire (&d->lock);
 

-

   /* Add block to free list. */
   list_push_front (&d->free_list, &b->free_elem);
 
   /* Add block to free list. */
   list_push_front (&d->free_list, &b->free_elem);
 


@@ -198,7 +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);


@@ -209,8 +228,16 @@ static struct arena *
 block_to_arena (struct block *b)
 {
   struct arena *a = pg_round_down (b);
 block_to_arena (struct block *b)
 {
   struct arena *a = pg_round_down (b);

+
+  /* Check that the arena is valid. */

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

+
+  /* Check that the block is properly aligned for the arena. */
+  ASSERT (a->desc == NULL
+          || (pg_ofs (b) - sizeof *a) % a->desc->block_size == 0);
+  ASSERT (a->desc != NULL || pg_ofs (b) == sizeof *a);
+

   return a;
 }
 
   return a;
 }