twom: use pointers to a pair of records rather than copying

cyrusimap · Dec 10, 2024 · 2a4c0a9 · 2a4c0a9
1 parent 816e822
commit 2a4c0a9
Showing 1 changed file with 40 additions and 38 deletions.
diff --git a/lib/cyrusdb_twom.c b/lib/cyrusdb_twom.c
@@ -192,6 +192,7 @@ struct dbengine {
 
     struct db_header header;
     struct skiploc loc;
+    struct skiprecord recs[2];
 
     /* tracking info */
     size_t end;
@@ -2267,8 +2268,8 @@ static int consistent(struct dbengine *db)
 /* perform some basic consistency checks */
 static int myconsistent(struct dbengine *db, struct txn *tid)
 {
-    struct skiprecord prevrecord;
-    struct skiprecord record;
+    struct skiprecord *prevp = &db->recs[0];
+    struct skiprecord *curp = &db->recs[1];
     size_t fwd[MAXLEVEL];
     size_t num_records = 0;
     size_t dirty_size = 0;
@@ -2279,81 +2280,82 @@ static int myconsistent(struct dbengine *db, struct txn *tid)
     assert(db->current_txn == tid); /* could both be null */
 
     /* read in the dummy */
-    r = read_onerecord(db, DUMMY_OFFSET, &prevrecord);
+    r = read_onerecord(db, DUMMY_OFFSET, prevp);
     if (r) return r;
 
     /* set up the location pointers */
     for (i = 0; i < MAXLEVEL; i++)
-        fwd[i] = _getloc(db, &prevrecord, i);
+        fwd[i] = _getloc(db, prevp, i);
 
     while (fwd[0]) {
-        r = read_onerecord(db, fwd[0], &record);
+        r = read_onerecord(db, fwd[0], curp);
         if (r) {
             xsyslog(LOG_ERR, "DBERROR: failed to read record for consistent",
                     "fname=<%s> offset=<%08llX>",
                     FNAME(db), (LLU)fwd[0]);
             return r;
         }
 
-        size_t ancestor = record.ancestor;
+        cmp = bsearch_ncompare_raw(KEY(db, curp), curp->keylen,
+                                   KEY(db, prevp), prevp->keylen);
+        if (cmp <= 0) {
+            xsyslog(LOG_ERR, "DBERROR: twom out of order",
+                    "fname=<%s> key=<%.*s> offset=<%08llX>"
+                    " prevkey=<%.*s> prevoffset=<%08llX)",
+                    FNAME(db), (int)curp->keylen, KEY(db, curp),
+                    (LLU)curp->offset,
+                    (int)prevp->keylen, KEY(db, prevp),
+                    (LLU)prevp->offset);
+            return CYRUSDB_INTERNAL;
+        }
+
+        size_t ancestor = curp->ancestor;
         while (ancestor) {
-            struct skiprecord parent;
-            r = read_onerecord(db, ancestor, &parent);
+            r = read_onerecord(db, ancestor, prevp);
             if (r) {
                 xsyslog(LOG_ERR, "DBERROR: failed to read ancestor for consistent",
                         "fname=<%s> key=<%.*s> offset=<%08llX>",
-                        FNAME(db), (int)record.keylen, KEY(db, &record),
+                        FNAME(db), (int)curp->keylen, KEY(db, curp),
                         (LLU)ancestor);
                 return r;
             }
-            cmp = bsearch_ncompare_raw(KEY(db, &record), record.keylen,
-                                       KEY(db, &parent), parent.keylen);
+            cmp = bsearch_ncompare_raw(KEY(db, curp), curp->keylen,
+                                       KEY(db, prevp), prevp->keylen);
             if (cmp) {
                 xsyslog(LOG_ERR, "DBERROR: twom mismatched ancestor",
                         "fname=<%s> key=<%.*s> offset=<%08llX>"
                         " parentkey=<%.*s> parentoffset=<%08llX)",
-                        FNAME(db), (int)record.keylen, KEY(db, &record),
-                        (LLU)record.offset,
-                        (int)parent.keylen, KEY(db, &parent),
-                        (LLU)parent.offset);
+                        FNAME(db), (int)curp->keylen, KEY(db, curp),
+                        (LLU)curp->offset,
+                        (int)prevp->keylen, KEY(db, prevp),
+                        (LLU)prevp->offset);
                 return CYRUSDB_INTERNAL;
             }
-            ancestor = parent.ancestor;
-            dirty_size += parent.len;
+            ancestor = prevp->ancestor;
+            dirty_size += prevp->len;
         }
 
-        cmp = bsearch_ncompare_raw(KEY(db, &record), record.keylen,
-                         KEY(db, &prevrecord), prevrecord.keylen);
-        if (cmp <= 0) {
-            xsyslog(LOG_ERR, "DBERROR: twom out of order",
-                    "fname=<%s> key=<%.*s> offset=<%08llX>"
-                    " prevkey=<%.*s> prevoffset=<%08llX)",
-                    FNAME(db), (int)record.keylen, KEY(db, &record),
-                    (LLU)record.offset,
-                    (int)prevrecord.keylen, KEY(db, &prevrecord),
-                    (LLU)prevrecord.offset);
-            return CYRUSDB_INTERNAL;
-        }
-
-        for (i = 0; i < record.level; i++) {
+        for (i = 0; i < curp->level; i++) {
             /* check the old pointer was to here */
-            if (fwd[i] != record.offset) {
+            if (fwd[i] != curp->offset) {
                 xsyslog(LOG_ERR, "DBERROR: twom broken linkage",
                                  "filename=<%s> offset=<%08llX> level=<%d>"
                                  " expected=<%08llX>",
-                                 FNAME(db), (LLU)record.offset, i, (LLU)fwd[i]);
+                                 FNAME(db), (LLU)curp->offset, i, (LLU)fwd[i]);
                 return CYRUSDB_INTERNAL;
             }
             /* and advance to the new pointer */
-            fwd[i] = _getloc(db, &record, i);
+            fwd[i] = _getloc(db, curp, i);
         }
 
-        /* keep a copy for comparison purposes */
-        prevrecord = record;
-
         // count if record or tombstone
-        if (record.type == DELETE) dirty_size += record.len;
+        if (curp->type == DELETE) dirty_size += curp->len;
         else num_records++;
+
+        /* switch pointers for next time */
+        struct skiprecord *temp = prevp;
+        prevp = curp;
+        curp = temp;
     }
 
     for (i = 0; i < MAXLEVEL; i++) {