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Hi.
In my attempt to port grub 2 to usparc, I had big problems with all the
memory allocation things, so I decided to rewrite the functions after
reading them (I wasn't able to understand at all 20% of the code).
Some comments :
It *seems* that before the alloc'ed chunks weren't linked any more with
other chunks. Now all the chunks of a region are part of the same ring.
Chunks were allocated from the end of the memory to the beginning, I
kept this behaviour.
It *seems* that the chunk headers were "forgotten" in the malloc
process, which led to my problems on usparc : a chunk was overwriting
the header of the previous one. It's now fixed.
A little schema to explain how it works :
First, we have a full free region, with the region header & chunk header:
( free )
[H_CHUNK ] (free, "next" points to self)
[H_REGION] ("head" always points to first chunk header)
We allocate a chunk that fit in the free space :
(alloc'ed)
[H_CHUNK ] (alloc, "next" points to free chunk)
( free )
[H_CHUNK ] (free, "next" points to alloc'ed chunk)
[H_REGION] (no change)
And so on.
Each chunk is 32 or 64 bits aligned (depends on arch) and his length is
a multiple of this alignment by giving some extra bytes to the alloc'ed
chunk if needed (its end is then also aligned, no byte loss).
I've added a defrag function that merges consecutive free chunks. It's
pretty fast (O(N), N=number of chunks) but I only call it when needed...
Maybe could it be interesting to call it on each grub_free().
I've added lots of dprintf calls triggered by "mm". They slows
everything down a lot...
I'm not sure where to put the 3 new prototypes, and I'm not even sure
about the name they should have. Please correct if it is wrong.
2005-07-11 Vincent Pelletier <[EMAIL PROTECTED]>
* kern/mm.c (GRUB_MM_ALIGN): Removed macro. Renamed
GRUB_MM_ALIGN_LOG2 into GRUB_MM_ALIGN.
(grub_defragment, align_before, align_after): New functions
and their prototypes.
(get_header_from_pointer): Check alignment correctly. Add
grub_dprintf call. Cast pointers so additions give the correct
result.
(grub_mm_init_region): Add dprintf calls. Compute size before
testing it. Only keep regions which can contain 1 or more
bytes.
(grub_real_malloc): Add grub_dprintf calls. Do some extra
sanity checks. Add grub_mm_dump calls. Change "for" loop into
"do..while". Don't change *first value. Keep alloc'ed headers
in the ring. Align beginning and end of alloc'ed chunks.
(grub_memalign): Add grub_dprintf calls. Add grub_mm_dump call.
Always align. Give the real wanted size to grub_real_malloc.
Use grub_defragment if needed.
(grub_free): Add grub_dprintf calls. Do some extra sanity
checks. Handle GRUB_MM_ALLOC_MAGIC in the ring correctly.
Call grub_fatal if the chunk to be freed isn't found.
(grub_realloc): Remove useless alignment things, since they
are handled in grub_real_malloc. Add (disabled) experimental
code to call grub_defragment if needed.
(grub_mm_dump): Follow the ring to be faster.
* include/grub/mm.h (MM_DEBUG): Changed default value to 0.
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Index: kern/mm.c
===================================================================
RCS file: /cvsroot/grub/grub2/kern/mm.c,v
retrieving revision 1.10
diff -u -p -r1.10 mm.c
--- kern/mm.c 23 Jun 2005 08:12:19 -0000 1.10
+++ kern/mm.c 11 Jul 2005 12:19:12 -0000
@@ -46,13 +46,11 @@ typedef struct grub_mm_header
*grub_mm_header_t;
#if GRUB_CPU_SIZEOF_VOID_P == 4
-# define GRUB_MM_ALIGN_LOG2 4
+# define GRUB_MM_ALIGN 4
#elif GRUB_CPU_SIZEOF_VOID_P == 8
-# define GRUB_MM_ALIGN_LOG2 8
+# define GRUB_MM_ALIGN 8
#endif
-#define GRUB_MM_ALIGN (1 << GRUB_MM_ALIGN_LOG2)
-
typedef struct grub_mm_region
{
struct grub_mm_header *first;
@@ -64,21 +62,45 @@ typedef struct grub_mm_region
+void grub_defragment (grub_mm_region_t r);
+grub_addr_t align_before (grub_addr_t addr, grub_size_t align);
+grub_addr_t align_after (grub_addr_t addr, grub_size_t align);
+
static grub_mm_region_t base;
+/* Align given memory address to the first valid position after addr.
+ If addr is already aligned, don't touch it. */
+grub_addr_t align_after (grub_addr_t addr, grub_size_t align)
+{
+ if (addr % align)
+ return addr + align - ( addr % align );
+ return addr;
+}
+
+/* Align given memory address to the first valid position before addr.
+ * If addr is already aligned, don't touch it. */
+grub_addr_t align_before (grub_addr_t addr, grub_size_t align)
+{
+ return addr - addr % align;
+}
+
/* Get a header from the pointer PTR, and set *P and *R to a pointer
to the header and a pointer to its region, respectively. PTR must
be allocated. */
static void
get_header_from_pointer (void *ptr, grub_mm_header_t *p, grub_mm_region_t *r)
{
- if ((grub_addr_t) ptr & (GRUB_MM_ALIGN - 1))
+ if ((grub_addr_t) ptr % GRUB_MM_ALIGN)
grub_fatal ("unaligned pointer %p", ptr);
for (*r = base; *r; *r = (*r)->next)
- if ((grub_addr_t) ptr > (*r)->addr
- && (grub_addr_t) ptr <= (*r)->addr + (*r)->size)
- break;
+ {
+ grub_dprintf ("mm", "[%p..%p]\n", ((*r)->addr),
+ ((grub_addr_t) (*r)->addr) + (*r)->size);
+ if ((grub_addr_t) ptr >= ((grub_addr_t) (*r)->addr)
+ && (grub_addr_t) ptr <= ((grub_addr_t) (*r)->addr) + (*r)->size)
+ break;
+ }
if (! *r)
grub_fatal ("out of range pointer %p", ptr);
@@ -96,27 +118,28 @@ grub_mm_init_region (void *addr, grub_si
grub_mm_header_t h;
grub_mm_region_t r, *p, q;
-#if 0
- grub_printf ("%s:%d: addr=%p, size=%u\n", __FILE__, __LINE__, addr, size);
-#endif
-
+ grub_dprintf ("mm", "New region (before) : %p:%x\n", addr, size);
+ r = (grub_mm_region_t) align_after ((grub_addr_t) addr, GRUB_MM_ALIGN);
+
+ size = align_before (size - sizeof (*r) -
+ ((grub_addr_t) r - (grub_addr_t) addr),
+ GRUB_MM_ALIGN);
+
/* If this region is too small, ignore it. */
- if (size < GRUB_MM_ALIGN * 2)
+ if (size < sizeof (grub_mm_header_t) + 1)
return;
- /* Allocate a region from the head. */
- r = (grub_mm_region_t) (((grub_addr_t) addr + GRUB_MM_ALIGN - 1)
- & (~(GRUB_MM_ALIGN - 1)));
- size -= (char *) r - (char *) addr + sizeof (*r);
-
- h = (grub_mm_header_t) ((char *) r + GRUB_MM_ALIGN);
+ h = (grub_mm_header_t) (r + 1);
h->next = h;
h->magic = GRUB_MM_FREE_MAGIC;
- h->size = (size >> GRUB_MM_ALIGN_LOG2);
+ h->size = size - sizeof (*h);
r->first = h;
r->addr = (grub_addr_t) h;
- r->size = (h->size << GRUB_MM_ALIGN_LOG2);
+ r->size = size;
+
+ grub_dprintf ("mm", "First header in new region : h=%p, size=%x\n",
+ h, h->size);
/* Find where to insert this region. Put a smaller one before bigger ones,
to prevent fragmentations. */
@@ -126,6 +149,7 @@ grub_mm_init_region (void *addr, grub_si
*p = r;
r->next = q;
+ grub_dprintf ("mm", "New region (after) : %p:%x:%p\n", r, size, r->next);
}
/* Allocate the number of units N with the alignment ALIGN from the ring
@@ -134,63 +158,87 @@ grub_mm_init_region (void *addr, grub_si
static void *
grub_real_malloc (grub_mm_header_t *first, grub_size_t n, grub_size_t align)
{
- grub_mm_header_t p, q;
+ grub_mm_header_t p, q, r;
+ grub_off_t extra = align_after (n, align) - n;
- if ((*first)->magic == GRUB_MM_ALLOC_MAGIC)
- return 0;
-
- for (q = *first, p = q->next; ; q = p, p = p->next)
+ if (! first)
+ grub_fatal ("null in the ring (at start)");
+
+ p = *first;
+
+ switch (p->magic)
{
- grub_off_t extra;
+ case GRUB_MM_ALLOC_MAGIC:
+ case GRUB_MM_FREE_MAGIC:
+ break;
+ default:
+#if MM_DEBUG
+ grub_mm_dump (__LINE__);
+#endif
+ grub_fatal ("magic is broken (at start) %p: 0x%x", p, p->magic);
+ }
- extra = ((grub_addr_t) (p + 1) >> GRUB_MM_ALIGN_LOG2) % align;
- if (extra)
- extra = align - extra;
+ do
+ {
+ q = p;
+ p = p->next;
if (! p)
grub_fatal ("null in the ring");
- if (p->magic != GRUB_MM_FREE_MAGIC)
- grub_fatal ("free magic is broken at %p: 0x%x", p, p->magic);
-
- if (p->size >= n + extra)
- {
- if (extra == 0 && p->size == n)
+ switch (p->magic)
+ {
+ case GRUB_MM_ALLOC_MAGIC:
+ break;
+ case GRUB_MM_FREE_MAGIC:
+ grub_dprintf ("mm", "Before: p %p:%x:%p\n",
+ p, p->size, p->next);
+ grub_dprintf ("mm", "Before: q %p:%x:%p\n",
+ q, q->size, q->next);
+ grub_dprintf ("mm", "Align = 0x%x Size = 0x%x Extra = 0x%x\n",
+ align, n, extra);
+ if (p->size == n + extra)
{
- q->next = p->next;
p->magic = GRUB_MM_ALLOC_MAGIC;
+ grub_dprintf ("mm", "After : p %p:%x:%p\n",
+ p, p->size, p->next);
+ grub_dprintf ("mm", "After : q %p:%x:%p\n",
+ q, q->size, q->next);
+ return p + 1;
}
- else if (extra == 0 || p->size == n + extra)
+ if (p->size >= n + extra + sizeof (*r))
{
- p->size -= n;
- p += p->size;
- p->size = n;
- p->magic = GRUB_MM_ALLOC_MAGIC;
- }
- else
- {
- grub_mm_header_t r;
-
- r = p + extra + n;
- r->magic = GRUB_MM_FREE_MAGIC;
- r->size = p->size - extra - n;
- r->next = p->next;
-
- p->size = extra;
- p->next = r;
- p += extra;
- p->size = n;
- p->magic = GRUB_MM_ALLOC_MAGIC;
- }
+#if 0
+ r = (grub_mm_header_t) align_before (
+ ((grub_addr_t) p) + p->size - (extra + n),
+ align);
+#else
+ /* XXX: Is it safe to assume we are aligned ? */
+ r = ((grub_addr_t) p) + p->size - (extra + n);
+#endif
+ r->magic = GRUB_MM_ALLOC_MAGIC;
+ r->size = n + extra;
+ r->next = p;
+ p->size = p->size - r->size - sizeof (*r);
+ q->next = r;
+
+ grub_dprintf ("mm", "After : p %p:%x:%p\n",
+ p, p->size, p->next);
+ grub_dprintf ("mm", "After : q %p:%x:%p\n",
+ q, q->size, q->next);
+ grub_dprintf ("mm", "After : r %p:%x:%p\n",
+ r, r->size, r->next);
+ return r + 1;
+ }
+ break;
+ default:
+#if MM_DEBUG
+ grub_mm_dump (__LINE__);
+#endif
+ grub_fatal ("magic is broken at %p: 0x%x", p, p->magic);
+ }
- *first = q;
-
- return p + 1;
- }
-
- if (p == *first)
- break;
- }
+ } while ( p != *first );
return 0;
}
@@ -200,12 +248,16 @@ void *
grub_memalign (grub_size_t align, grub_size_t size)
{
grub_mm_region_t r;
- grub_size_t n = ((size + GRUB_MM_ALIGN - 1) >> GRUB_MM_ALIGN_LOG2) + 1;
int count = 0;
- align = (align >> GRUB_MM_ALIGN_LOG2);
+#if 0
+ align = (align >> GRUB_MM_ALIGN);
if (align == 0)
align = 1;
+#else
+ /* XXX: Is it right to always align ? */
+ align = GRUB_MM_ALIGN;
+#endif
again:
@@ -213,9 +265,18 @@ grub_memalign (grub_size_t align, grub_s
{
void *p;
- p = grub_real_malloc (&(r->first), n, align);
+ p = grub_real_malloc (&(r->first), size, align);
if (p)
- return p;
+ {
+ grub_dprintf("mm","%p=malloc(0x%x)\n",p,size);
+#if MM_DEBUG
+ grub_size_t a;
+ for(a = 0; a < size; a++)
+ ((char *) p)[a] = 'X'; /* To test overlapping. */
+ grub_mm_dump (__LINE__);
+#endif
+ return p;
+ }
}
/* If failed, increase free memory somehow. */
@@ -228,6 +289,13 @@ grub_memalign (grub_size_t align, grub_s
goto again;
case 1:
+ /* Defragment memory. */
+ for (r = base; r; r = r->next)
+ grub_defragment (r);
+ count++;
+ goto again;
+
+ case 2:
/* Unload unneeded modules. */
grub_dl_unload_unneeded ();
count++;
@@ -248,6 +316,43 @@ grub_malloc (grub_size_t size)
return grub_memalign (0, size);
}
+/* Aggregates consecutive free segments. */
+void
+grub_defragment (grub_mm_region_t r)
+{
+ grub_mm_header_t p, first_free = 0;
+
+ grub_dprintf ("mm", "Defrag running...\n");
+
+ p = r->first;
+
+ do
+ {
+ p = p->next;
+ switch (p->magic)
+ {
+ case GRUB_MM_ALLOC_MAGIC:
+ first_free = 0;
+ break;
+ case GRUB_MM_FREE_MAGIC:
+ if (first_free)
+ {
+ first_free->next = p->next;
+ first_free->size += p->size + sizeof (*p);
+ }
+ else
+ first_free = p;
+ break;
+ default:
+#if MM_DEBUG
+ grub_mm_dump (__LINE__);
+#endif
+ grub_fatal ("magic is broken at %p: 0x%x", p, p->magic);
+ }
+ } while ( p != r->first );
+ grub_dprintf ("mm", "Done.\n");
+}
+
/* Deallocate the pointer PTR. */
void
grub_free (void *ptr)
@@ -258,60 +363,44 @@ grub_free (void *ptr)
if (! ptr)
return;
+ grub_dprintf ("mm", "free(%p)\n", ptr);
+
get_header_from_pointer (ptr, &p, &r);
- if (r->first->magic == GRUB_MM_ALLOC_MAGIC)
- {
- p->magic = GRUB_MM_FREE_MAGIC;
- r->first = p->next = p;
- }
- else
+ p = r->first;
+
+ do
{
- grub_mm_header_t q;
+ p = p->next;
-#if 0
- q = r->first;
- do
- {
- grub_printf ("%s:%d: q=%p, q->size=0x%x, q->magic=0x%x\n",
- __FILE__, __LINE__, q, q->size, q->magic);
- q = q->next;
- }
- while (q != r->first);
+ if (! p)
+ grub_fatal ("null in the ring");
+
+ switch (p->magic)
+ {
+ case GRUB_MM_ALLOC_MAGIC:
+ if (p + 1 != ptr)
+ continue;
+ else
+ {
+ p->magic = GRUB_MM_FREE_MAGIC;
+#if MM_DEBUG
+ grub_mm_dump (__LINE__);
+#endif
+ return;
+ }
+ case GRUB_MM_FREE_MAGIC:
+ continue;
+ default:
+#if MM_DEBUG
+ grub_mm_dump (__LINE__);
#endif
-
- for (q = r->first; q >= p || q->next <= p; q = q->next)
- {
- if (q->magic != GRUB_MM_FREE_MAGIC)
- grub_fatal ("free magic is broken at %p: 0x%x", q, q->magic);
-
- if (q >= q->next && (q < p || q->next > p))
- break;
- }
-
- p->magic = GRUB_MM_FREE_MAGIC;
- p->next = q->next;
- q->next = p;
-
- if (p + p->size == p->next)
- {
- if (p->next == q)
- q = p;
+ grub_fatal ("magic is broken at %p: 0x%x", p, p->magic);
+ }
+ } while ( p != r->first );
- p->next->magic = 0;
- p->size += p->next->size;
- p->next = p->next->next;
- }
-
- if (q + q->size == p)
- {
- p->magic = 0;
- q->size += p->size;
- q->next = p->next;
- }
+ grub_fatal ("alloc'ed chunk not found");
- r->first = q;
- }
}
/* Reallocate SIZE bytes and return the pointer. The contents will be
@@ -322,7 +411,6 @@ grub_realloc (void *ptr, grub_size_t siz
grub_mm_header_t p;
grub_mm_region_t r;
void *q;
- grub_size_t n;
if (! ptr)
return grub_malloc (size);
@@ -334,18 +422,33 @@ grub_realloc (void *ptr, grub_size_t siz
}
/* FIXME: Not optimal. */
- n = ((size + GRUB_MM_ALIGN - 1) >> GRUB_MM_ALIGN_LOG2) + 1;
get_header_from_pointer (ptr, &p, &r);
- if (p->size >= n)
+ if (p->size >= size)
return ptr;
+
+#if 0 /* XXX: Experimental. */
+ if(p->next->magic == GRUB_MM_FREE_MAGIC)
+ {
+ if (p->size + p->next->size < size)
+ grub_defragment (r); /* Try to increase the free space. */
+
+ if (p->size + p->next->size >= size)
+ {
+ grub_size_t delta = size - p->size;
+ p->next->size -= delta;
+ p->size += delta;
+ grub_memcpy (p->next, p->next + delta, sizeof(*p));
+ }
+ }
+#endif
q = grub_malloc (size);
- if (! q)
- return q;
-
- grub_memcpy (q, ptr, size);
- grub_free (ptr);
+ if (q)
+ {
+ grub_memcpy (q, ptr, size);
+ grub_free (ptr);
+ }
return q;
}
@@ -354,28 +457,29 @@ void
grub_mm_dump (unsigned lineno)
{
grub_mm_region_t r;
+ grub_mm_header_t p;
- grub_printf ("called at line %u\n", lineno);
+ grub_printf ("Dump called at line %u\n", lineno);
for (r = base; r; r = r->next)
{
- grub_mm_header_t p;
-
- for (p = (grub_mm_header_t) ((r->addr + GRUB_MM_ALIGN - 1)
- & (~(GRUB_MM_ALIGN - 1)));
- (grub_addr_t) p < r->addr + r->size;
- p++)
+ p = r->first;
+ do
{
switch (p->magic)
{
case GRUB_MM_FREE_MAGIC:
- grub_printf ("F:%p:%u:%p\n",
- p, p->size << GRUB_MM_ALIGN_LOG2, p->next);
+ grub_printf ("F:%p:%x:%p\n",
+ p, (grub_uintn_t) p->size, p->next);
break;
case GRUB_MM_ALLOC_MAGIC:
- grub_printf ("A:%p:%u\n", p, p->size << GRUB_MM_ALIGN_LOG2);
+ grub_printf ("A:%p:%x:%p\n", p, (grub_uintn_t) p->size, p->next);
break;
+ default:
+ grub_printf ("magic broken at %p\n", p);
+ return; /* XXX: A little rough. */
}
- }
+ p = p->next;
+ } while (p != r->first);
}
grub_printf ("\n");
Index: include/grub/mm.h
===================================================================
RCS file: /cvsroot/grub/grub2/include/grub/mm.h,v
retrieving revision 1.4
diff -u -p -r1.4 mm.h
--- include/grub/mm.h 20 Jan 2005 17:25:39 -0000 1.4
+++ include/grub/mm.h 11 Jul 2005 12:19:12 -0000
@@ -31,7 +31,7 @@ void *EXPORT_FUNC(grub_realloc) (void *p
void *EXPORT_FUNC(grub_memalign) (grub_size_t align, grub_size_t size);
/* For debugging. */
-#define MM_DEBUG 1
+#define MM_DEBUG 0
#if MM_DEBUG
void grub_mm_dump (unsigned lineno);
#endif
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