*/
struct metaheader
{
- /* Length (after this header). (FIXME: Could be in pages). */
+ /* Length (after this header). (FIXME: implied by page bits!). */
unsigned long metalen;
/* Next meta header, or 0 */
unsigned long next;
/* Bits start here. */
};
-#define BITS_PER_PAGE 2
-/* FIXME: Don't use page states for bitblock. It's tacky and confusing. */
-enum page_state
+/* Assumes a is a power of two. */
+static unsigned long align_up(unsigned long x, unsigned long a)
+{
+ return (x + a - 1) & ~(a - 1);
+}
+
+static unsigned long div_up(unsigned long x, unsigned long a)
+{
+ return (x + a - 1) / a;
+}
+
+/* It turns out that we spend a lot of time dealing with bit pairs.
+ * These routines manipulate them.
+ */
+static uint8_t get_bit_pair(const uint8_t *bits, unsigned long index)
+{
+ return bits[index * 2 / CHAR_BIT] >> (index * 2 % CHAR_BIT) & 3;
+}
+
+static void set_bit_pair(uint8_t *bits, unsigned long index, uint8_t val)
+{
+ bits[index * 2 / CHAR_BIT] &= ~(3 << (index * 2 % CHAR_BIT));
+ bits[index * 2 / CHAR_BIT] |= (val << (index * 2 % CHAR_BIT));
+}
+
+/* This is used for page states and subpage allocations */
+enum alloc_state
{
FREE,
TAKEN,
TAKEN_START,
- SUBPAGE,
+ SPECIAL, /* Sub-page allocation for page states. */
};
-/* Assumes a is a power of two. */
-static unsigned long align_up(unsigned long x, unsigned long a)
+/* The types for subpage metadata. */
+enum sub_metadata_type
{
- return (x + a - 1) & ~(a - 1);
+ /* FREE is same as alloc state */
+ BITMAP = 1,
+};
+
+/* Page states are represented by bitpairs, at the start of the pool. */
+#define BITS_PER_PAGE 2
+
+static enum alloc_state get_page_state(const void *pool, unsigned long page)
+{
+ return get_bit_pair(pool, page);
}
-static unsigned long div_up(unsigned long x, unsigned long a)
+static void set_page_state(void *pool, unsigned long page, enum alloc_state s)
{
- return (x + a - 1) / a;
+ set_bit_pair(pool, page, s);
}
/* The offset of metadata for a subpage allocation is found at the end
* of the subpage */
#define SUBPAGE_METAOFF (getpagesize() - sizeof(unsigned long))
-/* This is the length of metadata in bits. It consists of a TAKEN header,
- * then two bits for every BITMAP_GRANULARITY of usable bytes in the. */
+/* This is the length of metadata in bits. It consists of two bits
+ * for every BITMAP_GRANULARITY of usable bytes in the page, then two
+ * bits for the tailer.. */
#define BITMAP_METABITLEN \
- ((1 + div_up(SUBPAGE_METAOFF, BITMAP_GRANULARITY)) * BITS_PER_PAGE)
+ ((div_up(SUBPAGE_METAOFF, BITMAP_GRANULARITY) + 1) * BITS_PER_PAGE)
/* This is the length in bytes. */
#define BITMAP_METALEN (div_up(BITMAP_METABITLEN, CHAR_BIT))
-static enum page_state get_page_state(const uint8_t *bits, unsigned long page)
-{
- return bits[page * 2 / CHAR_BIT] >> (page * 2 % CHAR_BIT) & 3;
-}
-
-static void set_page_state(uint8_t *bits, unsigned long page, enum page_state s)
-{
- bits[page * 2 / CHAR_BIT] &= ~(3 << (page * 2 % CHAR_BIT));
- bits[page * 2 / CHAR_BIT] |= ((uint8_t)s << (page * 2 % CHAR_BIT));
-}
-
static struct metaheader *first_mheader(void *pool, unsigned long poolsize)
{
unsigned int pagestatelen;
set_page_state(pool, i, TAKEN);
}
-/* Two bits per element, representing page states. Returns 0 on fail. */
-static unsigned long alloc_from_bitmap(uint8_t *bits, unsigned long elems,
- unsigned long want, unsigned long align)
+/* Two bits per element, representing page states. Returns -1 on fail. */
+static long alloc_from_bitmap(uint8_t *bits, unsigned long elems,
+ unsigned long want, unsigned long align)
{
long i;
unsigned long free;
free = 0;
/* We allocate from far end, to increase ability to expand metadata. */
for (i = elems - 1; i >= 0; i--) {
- switch (get_page_state(bits, i)) {
+ switch (get_bit_pair(bits, i)) {
case FREE:
if (++free >= want) {
unsigned long j;
continue;
for (j = i+1; j < i + want; j++)
- set_page_state(bits, j, TAKEN);
- set_page_state(bits, i, TAKEN_START);
+ set_bit_pair(bits, j, TAKEN);
+ set_bit_pair(bits, i, TAKEN_START);
return i;
}
break;
- case SUBPAGE:
+ case SPECIAL:
case TAKEN_START:
case TAKEN:
free = 0;
}
}
- return 0;
+ return -1;
}
static unsigned long alloc_get_pages(void *pool, unsigned long poolsize,
return i;
}
break;
- case SUBPAGE:
+ case SPECIAL:
case TAKEN_START:
case TAKEN:
free = 0;
*metadata_off(pool, page) = meta - (uint8_t *)pool;
}
-static void *sub_page_alloc(void *pool, unsigned long page,
- unsigned long size, unsigned long align)
+static unsigned long sub_page_alloc(void *pool, unsigned long page,
+ unsigned long size, unsigned long align)
{
uint8_t *bits = get_page_metadata(pool, page);
- unsigned long i;
+ long i;
/* TAKEN at end means a bitwise alloc. */
- assert(get_page_state(bits, getpagesize()/BITMAP_GRANULARITY - 1)
- == TAKEN);
+ assert(get_bit_pair(bits, getpagesize()/BITMAP_GRANULARITY-1) == TAKEN);
/* Our bits are the same as the page bits. */
- i = alloc_from_bitmap(bits, getpagesize()/BITMAP_GRANULARITY,
+ i = alloc_from_bitmap(bits, SUBPAGE_METAOFF/BITMAP_GRANULARITY,
div_up(size, BITMAP_GRANULARITY),
align / BITMAP_GRANULARITY);
/* Can't allocate? */
- if (i == 0)
- return NULL;
+ if (i < 0)
+ return 0;
- return (char *)pool + page*getpagesize() + i*BITMAP_GRANULARITY;
+ return page*getpagesize() + i*BITMAP_GRANULARITY;
}
static uint8_t *alloc_metaspace(struct metaheader *mh, unsigned long bytes)
/* TAKEN tags end a subpage alloc. */
for (i = mh->metalen * CHAR_BIT / BITS_PER_PAGE - 1; i >= 0; i -= len) {
- switch (get_page_state(meta, i)) {
+ switch (get_bit_pair(meta, i)) {
case FREE:
len = 1;
free++;
return meta + i / (CHAR_BIT / BITS_PER_PAGE);
}
break;
- case TAKEN:
+ case BITMAP:
/* Skip over this allocated part. */
- len = BITMAP_METALEN * CHAR_BIT;
+ len = BITMAP_METALEN * CHAR_BIT / BITS_PER_PAGE;
free = 0;
break;
default:
/* OK, expand metadata, do it again. */
set_page_state(pool, nextpage / getpagesize(), TAKEN);
+ BUILD_ASSERT(FREE == 0);
memset((char *)pool + nextpage, 0, getpagesize());
mh->metalen += getpagesize();
return alloc_metaspace(mh, bytes);
newmh = (struct metaheader *)((char *)pool + page * getpagesize());
newmh->metalen = getpagesize() - sizeof(*mh);
+ BUILD_ASSERT(FREE == 0);
memset(newmh + 1, 0, newmh->metalen);
/* Sew it into linked list */
mh = first_mheader(pool,poolsize);
newmh->next = mh->next;
- mh->next = (char *)newmh - (char *)pool;
+ mh->next = pool_offset(pool, newmh);
return alloc_metaspace(newmh, bytes);
}
set_page_state(pool, pagenum, FREE);
}
-static void *alloc_sub_page(void *pool, unsigned long poolsize,
- unsigned long size, unsigned long align)
+static unsigned long alloc_sub_page(void *pool, unsigned long poolsize,
+ unsigned long size, unsigned long align)
{
unsigned long i;
uint8_t *metadata;
/* Look for partial page. */
for (i = 0; i < poolsize / getpagesize(); i++) {
- void *ret;
- if (get_page_state(pool, i) != SUBPAGE)
+ unsigned long ret;
+ if (get_page_state(pool, i) != SPECIAL)
continue;
ret = sub_page_alloc(pool, i, size, align);
/* Create new SUBPAGE page. */
i = alloc_get_pages(pool, poolsize, 1, 1);
if (i == 0)
- return NULL;
+ return 0;
/* Get metadata for page. */
metadata = new_metadata(pool, poolsize, BITMAP_METALEN);
if (!metadata) {
alloc_free_pages(pool, i);
- return NULL;
+ return 0;
}
- /* Actually, this is a SUBPAGE page now. */
- set_page_state(pool, i, SUBPAGE);
+ /* Actually, this is a subpage page now. */
+ set_page_state(pool, i, SPECIAL);
/* Set metadata pointer for page. */
set_page_metadata(pool, i, metadata);
return sub_page_alloc(pool, i, size, align);
}
+/* Returns true if we cleaned any pages. */
+static bool clean_empty_subpages(void *pool, unsigned long poolsize)
+{
+ unsigned long i;
+ bool progress = false;
+
+ for (i = 0; i < poolsize/getpagesize(); i++) {
+ uint8_t *meta;
+ unsigned int j;
+ if (get_page_state(pool, i) != SPECIAL)
+ continue;
+
+ meta = get_page_metadata(pool, i);
+ for (j = 0; j < SUBPAGE_METAOFF/BITMAP_GRANULARITY; j++)
+ if (get_page_state(meta, j) != FREE)
+ break;
+
+ /* So, is this page totally empty? */
+ if (j == SUBPAGE_METAOFF/BITMAP_GRANULARITY) {
+ set_page_state(pool, i, FREE);
+ progress = true;
+ }
+ }
+ return progress;
+}
+
+/* Returns true if we cleaned any pages. */
+static bool clean_metadata(void *pool, unsigned long poolsize)
+{
+ struct metaheader *mh, *prev_mh = NULL;
+ bool progress = false;
+
+ for (mh = first_mheader(pool,poolsize); mh; mh = next_mheader(pool,mh)){
+ uint8_t *meta;
+ long i;
+
+ meta = (uint8_t *)(mh + 1);
+ BUILD_ASSERT(FREE == 0);
+ for (i = mh->metalen - 1; i > 0; i--)
+ if (meta[i] != 0)
+ break;
+
+ /* Completely empty? */
+ if (prev_mh && i == mh->metalen) {
+ alloc_free_pages(pool,
+ pool_offset(pool, mh)/getpagesize());
+ prev_mh->next = mh->next;
+ mh = prev_mh;
+ progress = true;
+ } else {
+ uint8_t *p;
+
+ /* Some pages at end are free? */
+ for (p = (uint8_t *)(mh+1)+mh->metalen - getpagesize();
+ p > meta + i;
+ p -= getpagesize()) {
+ set_page_state(pool,
+ pool_offset(pool, p)
+ / getpagesize(),
+ FREE);
+ progress = true;
+ }
+ }
+ }
+
+ return progress;
+}
+
void *alloc_get(void *pool, unsigned long poolsize,
unsigned long size, unsigned long align)
{
+ bool subpage_clean = false, metadata_clean = false;
+ unsigned long ret;
+
if (poolsize < MIN_SIZE)
return NULL;
- /* Sub-page allocations have an overhead of 25%. */
- if (size + size/4 >= getpagesize() || align >= getpagesize()) {
- unsigned long ret, pages = div_up(size, getpagesize());
+again:
+ /* Sub-page allocations have an overhead of ~12%. */
+ if (size + size/8 >= getpagesize() || align >= getpagesize()) {
+ unsigned long pages = div_up(size, getpagesize());
- ret = alloc_get_pages(pool, poolsize, pages, align);
- if (ret == 0)
- return NULL;
- return (char *)pool + ret * getpagesize();
+ ret = alloc_get_pages(pool, poolsize, pages, align)
+ * getpagesize();
+ } else
+ ret = alloc_sub_page(pool, poolsize, size, align);
+
+ if (ret != 0)
+ return (char *)pool + ret;
+
+ /* Allocation failed: garbage collection. */
+ if (!subpage_clean) {
+ subpage_clean = true;
+ if (clean_empty_subpages(pool, poolsize))
+ goto again;
+ }
+
+ if (!metadata_clean) {
+ metadata_clean = true;
+ if (clean_metadata(pool, poolsize))
+ goto again;
}
- return alloc_sub_page(pool, poolsize, size, align);
+ /* FIXME: Compact metadata? */
+ return NULL;
}
static void subpage_free(void *pool, unsigned long pagenum, void *free)
while (off < SUBPAGE_METAOFF / BITMAP_GRANULARITY
&& get_page_state(metadata, off) == TAKEN)
set_page_state(metadata, off++, FREE);
-
- /* FIXME: If whole page free, free page and metadata. */
}
void alloc_free(void *pool, unsigned long poolsize, void *free)
pagenum = pool_offset(pool, free) / getpagesize();
- if (get_page_state(pool, pagenum) == SUBPAGE)
+ if (get_page_state(pool, pagenum) == SPECIAL)
subpage_free(pool, pagenum, free);
else {
assert((unsigned long)free % getpagesize() == 0);
{
unsigned long *mhoff = metadata_off(pool, page);
unsigned int i;
- enum page_state last_state = FREE;
+ enum alloc_state last_state = FREE;
if (*mhoff + sizeof(struct metaheader) > poolsize)
return false;
return false;
/* Marker at end of subpage allocation is "taken" */
- if (get_page_state((uint8_t *)pool + *mhoff,
- getpagesize()/BITMAP_GRANULARITY - 1) != TAKEN)
+ if (get_bit_pair((uint8_t *)pool + *mhoff,
+ getpagesize()/BITMAP_GRANULARITY - 1) != TAKEN)
return false;
for (i = 0; i < SUBPAGE_METAOFF / BITMAP_GRANULARITY; i++) {
- enum page_state state;
+ enum alloc_state state;
- state = get_page_state((uint8_t *)pool + *mhoff, i);
+ state = get_bit_pair((uint8_t *)pool + *mhoff, i);
switch (state) {
- case SUBPAGE:
+ case SPECIAL:
return false;
case TAKEN:
if (last_state == FREE)
{
unsigned long i;
struct metaheader *mh;
- enum page_state last_state = FREE;
+ enum alloc_state last_state = FREE;
bool was_metadata = false;
if (poolsize < MIN_SIZE)
}
for (i = 0; i < poolsize / getpagesize(); i++) {
- enum page_state state = get_page_state(pool, i);
+ enum alloc_state state = get_page_state(pool, i);
bool is_metadata = is_metadata_page(pool, poolsize,i);
switch (state) {
if (is_metadata != was_metadata)
return false;
break;
- case SUBPAGE:
+ case SPECIAL:
/* Check metadata pointer etc. */
if (!check_subpage(pool, poolsize, i))
return false;
}
return true;
}
+
+void alloc_visualize(FILE *out, void *pool, unsigned long poolsize)
+{
+ struct metaheader *mh;
+ unsigned long pagebitlen, metadata_pages, count[1<<BITS_PER_PAGE], tot;
+ long i;
+
+ if (poolsize < MIN_SIZE) {
+ fprintf(out, "Pool smaller than %u: no content\n", MIN_SIZE);
+ return;
+ }
+
+ memset(count, 0, sizeof(count));
+ for (i = 0; i < poolsize / getpagesize(); i++)
+ count[get_page_state(pool, i)]++;
+
+ mh = first_mheader(pool, poolsize);
+ pagebitlen = (char *)mh - (char *)pool;
+ fprintf(out, "%lu bytes of page bits: FREE/TAKEN/TAKEN_START/SUBPAGE = %lu/%lu/%lu/%lu\n",
+ pagebitlen, count[0], count[1], count[2], count[3]);
+
+ /* One metadata page for every page of page bits. */
+ metadata_pages = div_up(pagebitlen, getpagesize());
+
+ /* Now do each metadata page. */
+ for (; mh; mh = next_mheader(pool,mh)) {
+ unsigned long free = 0, subpageblocks = 0, len = 0;
+ uint8_t *meta = (uint8_t *)(mh + 1);
+
+ metadata_pages += (sizeof(*mh) + mh->metalen) / getpagesize();
+
+ /* TAKEN tags end a subpage alloc. */
+ for (i = mh->metalen * CHAR_BIT/BITS_PER_PAGE - 1;
+ i >= 0;
+ i -= len) {
+ switch (get_page_state(meta, i)) {
+ case FREE:
+ len = 1;
+ free++;
+ break;
+ case TAKEN:
+ /* Skip over this allocated part. */
+ len = BITMAP_METALEN * CHAR_BIT;
+ subpageblocks++;
+ break;
+ default:
+ assert(0);
+ }
+ }
+
+ fprintf(out, "Metadata %lu-%lu: %lu free, %lu subpageblocks, %lu%% density\n",
+ pool_offset(pool, mh),
+ pool_offset(pool, (char *)(mh+1) + mh->metalen),
+ free, subpageblocks,
+ subpageblocks * BITMAP_METALEN * 100
+ / (free + subpageblocks * BITMAP_METALEN));
+ }
+
+ /* Account for total pages allocated. */
+ tot = (count[1] + count[2] - metadata_pages) * getpagesize();
+
+ fprintf(out, "Total metadata bytes = %lu\n",
+ metadata_pages * getpagesize());
+
+ /* Now do every subpage. */
+ for (i = 0; i < poolsize / getpagesize(); i++) {
+ uint8_t *meta;
+ unsigned int j;
+ if (get_page_state(pool, i) != SPECIAL)
+ continue;
+
+ memset(count, 0, sizeof(count));
+ meta = get_page_metadata(pool, i);
+ for (j = 0; j < SUBPAGE_METAOFF/BITMAP_GRANULARITY; j++)
+ count[get_page_state(meta, j)]++;
+
+ fprintf(out, "Subpage %lu: "
+ "FREE/TAKEN/TAKEN_START = %lu/%lu/%lu %lu%% density\n",
+ i, count[0], count[1], count[2],
+ ((count[1] + count[2]) * BITMAP_GRANULARITY) * 100
+ / getpagesize());
+ tot += (count[1] + count[2]) * BITMAP_GRANULARITY;
+ }
+
+ /* This is optimistic, since we overalloc in several cases. */
+ fprintf(out, "Best possible allocation density = %lu%%\n",
+ tot * 100 / poolsize);
+}
projects / ccan / blobdiff