ovsdb-data: Deduplicate string atoms.

ovsdb-server spends a lot of time cloning atoms for various reasons,
e.g. to create a diff of two rows or to clone a row to the transaction.
All atoms, except for strings, contains a simple value that could be
copied in efficient way, but duplicating strings every time has a
significant performance impact.

Introducing a new reference-counted structure 'ovsdb_atom_string'
that allows to not copy strings every time, but just increase a
reference counter.

This change allows to increase transaction throughput in benchmarks
up to 2x for standalone databases and 3x for clustered databases, i.e.
number of transactions that ovsdb-server can handle per second.
It also noticeably reduces memory consumption of ovsdb-server.

Next step will be to consolidate this structure with json strings,
so we will not need to duplicate strings while converting database
objects to json and back.

Signed-off-by: Ilya Maximets <i.maximets@ovn.org>
Acked-by: Dumitru Ceara <dceara@redhat.com>
Acked-by: Mark D. Gray <mark.d.gray@redhat.com>

1 files changed, 8 insertions, 6 deletions

diff --git a/tests/test-ovsdb.c b/tests/test-ovsdb.c
index 86d75dfd9..432977159 100644
--- a/tests/test-ovsdb.c
+++ b/tests/test-ovsdb.c
@@ -2744,13 +2744,15 @@ print_idl_row_simple2(const struct idltest_simple2 *s, int step)
     printf("%03d: name=%s smap=[",
            step, s->name);
     for (i = 0; i < smap->n; i++) {
-        printf("[%s : %s]%s", smap->keys[i].string, smap->values[i].string,
-                i < smap->n-1? ",": "");
+        printf("[%s : %s]%s",
+               smap->keys[i].s->string, smap->values[i].s->string,
+               i < smap->n - 1 ? "," : "");
     }
     printf("] imap=[");
     for (i = 0; i < imap->n; i++) {
-        printf("[%"PRId64" : %s]%s", imap->keys[i].integer, imap->values[i].string,
-                i < imap->n-1? ",":"");
+        printf("[%"PRId64" : %s]%s",
+               imap->keys[i].integer, imap->values[i].s->string,
+               i < imap->n - 1 ? "," : "");
     }
     printf("]\n");
 }
@@ -2819,8 +2821,8 @@ do_idl_partial_update_map_column(struct ovs_cmdl_context *ctx)
     myTxn = ovsdb_idl_txn_create(idl);
     smap = idltest_simple2_get_smap(myRow, OVSDB_TYPE_STRING,
                                     OVSDB_TYPE_STRING);
-    strcpy(key_to_delete, smap->keys[0].string);
-    idltest_simple2_update_smap_delkey(myRow, smap->keys[0].string);
+    ovs_strlcpy(key_to_delete, smap->keys[0].s->string, sizeof key_to_delete);
+    idltest_simple2_update_smap_delkey(myRow, smap->keys[0].s->string);
     ovsdb_idl_txn_commit_block(myTxn);
     ovsdb_idl_txn_destroy(myTxn);
     ovsdb_idl_get_initial_snapshot(idl);