#include "tdb_private.h"
+/* 'right' merges can involve O(n^2) cost when combined with a
+ traverse, so they are disabled until we find a way to do them in
+ O(1) time
+*/
+#define USE_RIGHT_MERGES 0
+
/* read a freelist record and check for simple errors */
int tdb_rec_free_read(struct tdb_context *tdb, tdb_off_t off, struct list_struct *rec)
{
}
-
+#if USE_RIGHT_MERGES
/* Remove an element from the freelist. Must have alloc lock. */
static int remove_from_freelist(struct tdb_context *tdb, tdb_off_t off, tdb_off_t next)
{
TDB_LOG((tdb, TDB_DEBUG_FATAL,"remove_from_freelist: not on list at off=%d\n", off));
return TDB_ERRCODE(TDB_ERR_CORRUPT, -1);
}
+#endif
/* update a record tailer (must hold allocation lock) */
neccessary. */
int tdb_free(struct tdb_context *tdb, tdb_off_t offset, struct list_struct *rec)
{
- tdb_off_t right, left;
-
/* Allocation and tailer lock */
if (tdb_lock(tdb, -1, F_WRLCK) != 0)
return -1;
goto fail;
}
+#if USE_RIGHT_MERGES
/* Look right first (I'm an Australian, dammit) */
- right = offset + sizeof(*rec) + rec->rec_len;
- if (right + sizeof(*rec) <= tdb->map_size) {
+ if (offset + sizeof(*rec) + rec->rec_len + sizeof(*rec) <= tdb->map_size) {
+ tdb_off_t right = offset + sizeof(*rec) + rec->rec_len;
struct list_struct r;
if (tdb->methods->tdb_read(tdb, right, &r, sizeof(r), DOCONV()) == -1) {
goto left;
}
rec->rec_len += sizeof(r) + r.rec_len;
+ if (update_tailer(tdb, offset, rec) == -1) {
+ TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_free: update_tailer failed at %u\n", offset));
+ goto fail;
+ }
}
}
-
left:
+#endif
+
/* Look left */
- left = offset - sizeof(tdb_off_t);
- if (left > TDB_DATA_START(tdb->header.hash_size)) {
+ if (offset - sizeof(tdb_off_t) > TDB_DATA_START(tdb->header.hash_size)) {
+ tdb_off_t left = offset - sizeof(tdb_off_t);
struct list_struct l;
tdb_off_t leftsize;
left = offset - leftsize;
- /* Now read in record */
+ if (leftsize > offset ||
+ left < TDB_DATA_START(tdb->header.hash_size)) {
+ goto update;
+ }
+
+ /* Now read in the left record */
if (tdb->methods->tdb_read(tdb, left, &l, sizeof(l), DOCONV()) == -1) {
TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_free: left read failed at %u (%u)\n", left, leftsize));
goto update;
/* If it's free, expand to include it. */
if (l.magic == TDB_FREE_MAGIC) {
- if (remove_from_freelist(tdb, left, l.next) == -1) {
- TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_free: left free failed at %u\n", left));
- goto update;
- } else {
- offset = left;
- rec->rec_len += leftsize;
+ /* we now merge the new record into the left record, rather than the other
+ way around. This makes the operation O(1) instead of O(n). This change
+ prevents traverse from being O(n^2) after a lot of deletes */
+ l.rec_len += sizeof(*rec) + rec->rec_len;
+ if (tdb_rec_write(tdb, left, &l) == -1) {
+ TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_free: update_left failed at %u\n", left));
+ goto fail;
}
+ if (update_tailer(tdb, left, &l) == -1) {
+ TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_free: update_tailer failed at %u\n", offset));
+ goto fail;
+ }
+ tdb_unlock(tdb, -1, F_WRLCK);
+ return 0;
}
}
update:
- if (update_tailer(tdb, offset, rec) == -1) {
- TDB_LOG((tdb, TDB_DEBUG_FATAL, "tdb_free: update_tailer failed at %u\n", offset));
- goto fail;
- }
/* Now, prepend to free list */
rec->magic = TDB_FREE_MAGIC;
tdb_off_t rec_ptr, last_ptr;
tdb_len_t rec_len;
} bestfit;
+ float multiplier = 1.0;
if (tdb_lock(tdb, -1, F_WRLCK) == -1)
return 0;
bestfit.rec_len = rec->rec_len;
bestfit.rec_ptr = rec_ptr;
bestfit.last_ptr = last_ptr;
- /* consider a fit to be good enough if
- we aren't wasting more than half
- the space */
- if (bestfit.rec_len < 2*length) {
- break;
- }
}
}
/* move to the next record */
last_ptr = rec_ptr;
rec_ptr = rec->next;
+
+ /* if we've found a record that is big enough, then
+ stop searching if its also not too big. The
+ definition of 'too big' changes as we scan
+ through */
+ if (bestfit.rec_len > 0 &&
+ bestfit.rec_len < length * multiplier) {
+ break;
+ }
+
+ /* this multiplier means we only extremely rarely
+ search more than 50 or so records. At 50 records we
+ accept records up to 11 times larger than what we
+ want */
+ multiplier *= 1.05;
}
if (bestfit.rec_ptr != 0) {
return 0;
}
+
+
+/*
+ return the size of the freelist - used to decide if we should repack
+*/
+int tdb_freelist_size(struct tdb_context *tdb)
+{
+ tdb_off_t ptr;
+ int count=0;
+
+ if (tdb_lock(tdb, -1, F_RDLCK) == -1) {
+ return -1;
+ }
+
+ ptr = FREELIST_TOP;
+ while (tdb_ofs_read(tdb, ptr, &ptr) == 0 && ptr != 0) {
+ count++;
+ }
+
+ tdb_unlock(tdb, -1, F_RDLCK);
+ return count;
+}
git.samba.org / ira / wip.git / blobdiff