return ilog64(val);
}
+static unsigned ffs64(uint64_t val)
+{
+#if HAVE_BUILTIN_FFSLL
+ return __builtin_ffsll(val);
+#else
+ unsigned r = 0;
+
+ if (!val)
+ return 0;
+
+ if (!(val & 0xffffffff)) {
+ val >>= 32;
+ r += 32;
+ }
+ if (!(val & 0xffff)) {
+ val >>= 16;
+ r += 16;
+ }
+ if (!(val & 0xff)) {
+ val >>= 8;
+ r += 8;
+ }
+ if (!(val & 0xf)) {
+ val >>= 4;
+ r += 4;
+ }
+ if (!(val & 0x3)) {
+ val >>= 2;
+ r += 2;
+ }
+ if (!(val & 0x1)) {
+ val >>= 1;
+ r += 1;
+ }
+ return r;
+#endif
+}
+
/* In which bucket would we find a particular record size? (ignoring header) */
unsigned int size_to_bucket(unsigned int zone_bits, tdb_len_t data_len)
{
return bucket;
}
-/* Subtract 1-byte tailer and header. Then round up to next power of 2. */
-static unsigned max_zone_bits(struct tdb_context *tdb)
+/* Binary search for the zone for this offset. */
+static tdb_off_t off_to_zone(struct tdb_context *tdb, tdb_off_t off,
+ struct free_zone_header *zhdr)
{
- return fls64(tdb->map_size-1-sizeof(struct tdb_header)-1) + 1;
-}
+ tdb_off_t start, end;
-/* Start by using a random zone to spread the load: returns the offset. */
-static uint64_t random_zone(struct tdb_context *tdb)
-{
- struct free_zone_header zhdr;
- tdb_off_t off = sizeof(struct tdb_header);
- tdb_len_t half_bits;
- uint64_t randbits = 0;
- unsigned int i;
+ start = sizeof(struct tdb_header);
+ end = start + (1ULL << fls64(tdb->map_size - start));
- for (i = 0; i < 64; i += fls64(RAND_MAX))
- randbits ^= ((uint64_t)random()) << i;
-
- /* FIXME: Does this work? Test! */
- half_bits = max_zone_bits(tdb) - 1;
- do {
- /* Pick left or right side (not outside file) */
- if ((randbits & 1)
- && !tdb->methods->oob(tdb, off + (1ULL << half_bits)
- + sizeof(zhdr), true)) {
- off += 1ULL << half_bits;
- }
- randbits >>= 1;
-
- if (tdb_read_convert(tdb, off, &zhdr, sizeof(zhdr)) == -1)
+ for (;;) {
+ if (tdb_read_convert(tdb, start, zhdr, sizeof(*zhdr)) == -1)
return TDB_OFF_ERR;
- if (zhdr.zone_bits == half_bits)
- return off;
+ /* Is it inside this zone? */
+ if (off < start + (1ULL << zhdr->zone_bits))
+ return start;
- half_bits--;
- } while (half_bits >= INITIAL_ZONE_BITS);
+ /* In practice, start + end won't overflow. */
+ if (off >= (start + end) / 2)
+ start = (start + end) / 2;
+ else
+ end = (start + end) / 2;
+ }
+}
- tdb->ecode = TDB_ERR_CORRUPT;
- tdb->log(tdb, TDB_DEBUG_FATAL, tdb->log_priv,
- "random_zone: zone at %llu smaller than %u bits?",
- (long long)off, INITIAL_ZONE_BITS);
- return TDB_OFF_ERR;
+static tdb_off_t last_zone(struct tdb_context *tdb,
+ struct free_zone_header *zhdr)
+{
+ return off_to_zone(tdb, tdb->map_size - 1, zhdr);
}
int tdb_zone_init(struct tdb_context *tdb)
{
- tdb->zone_off = random_zone(tdb);
+ unsigned int i;
+ uint64_t randoff = 0;
+
+ /* We start in a random zone, to spread the load. */
+ for (i = 0; i < 64; i += fls64(RAND_MAX))
+ randoff ^= ((uint64_t)random()) << i;
+ randoff = sizeof(struct tdb_header)
+ + (randoff % (tdb->map_size - sizeof(struct tdb_header)));
+
+ tdb->zone_off = off_to_zone(tdb, randoff, &tdb->zhdr);
if (tdb->zone_off == TDB_OFF_ERR)
return -1;
- if (tdb_read_convert(tdb, tdb->zone_off,
- &tdb->zhdr, sizeof(tdb->zhdr)) == -1)
- return -1;
return 0;
}
int ret;
assert(len_with_header >= sizeof(new));
- assert(zone_bits < (1 << 6));
+ assert(zone_bits < 64);
new.magic_and_meta = TDB_FREE_MAGIC | zone_bits;
new.data_len = len_with_header - sizeof(struct tdb_used_record);
tdb_off_t off, tdb_off_t b_off, tdb_len_t data_len)
{
struct tdb_free_record pad, *r;
- tdb_off_t end = off + sizeof(struct tdb_used_record) + data_len;
+ tdb_off_t zone_end, end;
+
+ end = off + sizeof(struct tdb_used_record) + data_len;
+ zone_end = zone_off + (1ULL << zone_bits);
- while (end < (zone_off + (1ULL << zone_bits))) {
+ if (tdb->methods->oob(tdb, zone_end, true))
+ zone_end = tdb->map_size;
+
+ while (end < zone_end) {
tdb_off_t nb_off;
/* FIXME: do tdb_get here and below really win? */
return 0;
}
-static bool zones_happy(struct tdb_context *tdb)
+static bool zones_contended(struct tdb_context *tdb)
{
- /* FIXME: look at distribution of zones. */
- return true;
+ return false;
}
/* Assume we want buckets up to the comfort factor. */
{
uint64_t old_size;
tdb_off_t off;
- uint8_t zone_bits;
- unsigned int num_buckets;
- tdb_len_t wanted;
+ unsigned int num_buckets, zone_bits;
+ tdb_len_t wanted, expand;
struct free_zone_header zhdr;
- bool enlarge_zone;
/* We need room for the record header too. */
wanted = sizeof(struct tdb_used_record) + size;
if (tdb->map_size != old_size)
goto success;
- /* FIXME: Tailer is a bogus optimization, remove it. */
- /* zone bits tailer char is protected by EXPAND lock. */
- if (tdb->methods->read(tdb, old_size - 1, &zone_bits, 1) == -1)
+ /* Treat last zone as minimum reasonable zone size. */
+ off = last_zone(tdb, &zhdr);
+ if (off == TDB_OFF_ERR)
goto fail;
- /* If zones aren't working well, add larger zone if possible. */
- enlarge_zone = !zones_happy(tdb);
+ /* Zone isn't fully expanded? */
+ if (tdb->map_size < off + (1ULL << zhdr.zone_bits)) {
+ expand = off + (1ULL << zhdr.zone_bits) - tdb->map_size;
+ /* Expand more than we want. */
+ if (expand > (wanted << TDB_COMFORT_FACTOR_BITS))
+ expand = (wanted << TDB_COMFORT_FACTOR_BITS);
+ if (tdb->methods->expand_file(tdb, expand) == -1)
+ goto fail;
+ /* We need to drop this lock before adding free record. */
+ tdb_unlock_expand(tdb, F_WRLCK);
+
+ /* Allocate from here. */
+ tdb->zone_off = off;
+ tdb->zhdr = zhdr;
+
+ /* FIXME: If this isn't sufficient, we search again... */
+ return add_free_record(tdb, zhdr.zone_bits,
+ tdb->map_size - expand, expand);
+ }
- /* New zone can be between zone_bits or larger if we're on the right
- * boundary. */
- for (;;) {
- /* Does this fit the allocation comfortably? */
- if ((1ULL << zone_bits) >= overhead(zone_bits) + wanted) {
- /* Only let enlarge_zone enlarge us once. */
- if (!enlarge_zone)
- break;
- enlarge_zone = false;
- }
- if ((old_size - 1 - sizeof(struct tdb_header))
- & (1 << zone_bits))
- break;
- zone_bits++;
+ /* We are never allowed to cross a power-of-two boundary, and our
+ * minimum zone size is 1 << INITIAL_ZONE_BITS.
+ *
+ * If our filesize is 128k, we can add a 64k or a 128k zone. If it's
+ * 192k, we can only add a 64k zone.
+ *
+ * In other words, our max zone size is (1 << (ffs(filesize) - 1)) */
+ zone_bits = ffs64(old_size - sizeof(struct tdb_header)) - 1;
+ assert(zone_bits >= INITIAL_ZONE_BITS);
+
+ /* Big zones generally good, but more zones wanted if contended. */
+ if (zones_contended(tdb)) {
+ /* If it suffices, make zone same size as last one. */
+ if (zhdr.zone_bits < zone_bits
+ && (1ULL << zhdr.zone_bits) >= overhead(zone_bits)+wanted)
+ zone_bits = zhdr.zone_bits;
}
zhdr.zone_bits = zone_bits;
num_buckets = BUCKETS_FOR_ZONE(zone_bits);
- /* FIXME: I don't think we need to expand to full zone, do we? */
- if (tdb->methods->expand_file(tdb, 1ULL << zone_bits) == -1)
- goto fail;
+ /* Expand the file by more than we need right now. */
+ expand = 1ULL << zone_bits;
+ if (expand > overhead(zone_bits) + (wanted << TDB_COMFORT_FACTOR_BITS))
+ expand = overhead(zone_bits)
+ + (wanted << TDB_COMFORT_FACTOR_BITS);
- /* Write new tailer. */
- if (tdb->methods->write(tdb, tdb->map_size - 1, &zone_bits, 1) == -1)
+ if (tdb->methods->expand_file(tdb, expand) == -1)
goto fail;
- /* Write new zone header (just before old tailer). */
- off = old_size - 1;
+ /* Write new zone header (at old end). */
+ off = old_size;
if (tdb_write_convert(tdb, off, &zhdr, sizeof(zhdr)) == -1)
goto fail;
off += (num_buckets+1) * sizeof(tdb_off_t);
/* Now add the rest as our free record. */
- if (add_free_record(tdb, zone_bits, off, tdb->map_size-1-off) == -1)
+ if (add_free_record(tdb, zone_bits, off, expand - overhead(zone_bits))
+ == -1)
goto fail;
/* Try allocating from this zone now. */
- tdb->zone_off = old_size - 1;
+ tdb->zone_off = old_size;
tdb->zhdr = zhdr;
success:
projects / ccan / blobdiff