json: echo: Speedup seqnum_to_json()

Derek Dai reports:
"If there are a lot of command in JSON node, seqnum_to_json() will slow
down application (eg: firewalld) dramatically since it iterate whole
command list every time."

He sent a patch implementing a lookup table, but we can do better: Speed
this up by introducing a hash table to store the struct json_cmd_assoc
objects in, taking their netlink sequence number as key.

Quickly tested restoring a ruleset containing about 19k rules:

| # time ./before/nft -jeaf large_ruleset.json >/dev/null
| 4.85user 0.47system 0:05.48elapsed 97%CPU (0avgtext+0avgdata 69732maxresident)k
| 0inputs+0outputs (15major+16937minor)pagefaults 0swaps

| # time ./after/nft -jeaf large_ruleset.json >/dev/null
| 0.18user 0.44system 0:00.70elapsed 89%CPU (0avgtext+0avgdata 68484maxresident)k
| 0inputs+0outputs (15major+16645minor)pagefaults 0swaps

Bugzilla: https://bugzilla.netfilter.org/show_bug.cgi?id=1479
Reported-by: Derek Dai <daiderek@gmail.com>
Signed-off-by: Phil Sutter <phil@nwl.cc>

diff --git a/src/parser_json.c b/src/parser_json.c
index b1de56a4a0d27f8ba0ed944c5719b82f7e18971a..6ebbb408d68390ac2eed76f56ae6efdcb2c4132f 100644 (file)
--- a/src/parser_json.c
+++ b/src/parser_json.c
@@ -3762,42 +3762,50 @@ static int json_verify_metainfo(struct json_ctx *ctx, json_t *root)
 }
 
 struct json_cmd_assoc {
-       struct json_cmd_assoc *next;
+       struct hlist_node hnode;
        const struct cmd *cmd;
        json_t *json;
 };
 
-static struct json_cmd_assoc *json_cmd_list = NULL;
+#define CMD_ASSOC_HSIZE                512
+static struct hlist_head json_cmd_assoc_hash[CMD_ASSOC_HSIZE];
 
 static void json_cmd_assoc_free(void)
 {
        struct json_cmd_assoc *cur;
+       struct hlist_node *pos, *n;
+       int i;
 
-       while (json_cmd_list) {
-               cur = json_cmd_list;
-               json_cmd_list = cur->next;
-               free(cur);
+       for (i = 0; i < CMD_ASSOC_HSIZE; i++) {
+               hlist_for_each_entry_safe(cur, pos, n,
+                                         &json_cmd_assoc_hash[i], hnode)
+                       free(cur);
        }
 }
 
 static void json_cmd_assoc_add(json_t *json, const struct cmd *cmd)
 {
        struct json_cmd_assoc *new = xzalloc(sizeof *new);
+       int key = cmd->seqnum % CMD_ASSOC_HSIZE;
 
-       new->next       = json_cmd_list;
        new->json       = json;
        new->cmd        = cmd;
-       json_cmd_list   = new;
+
+       hlist_add_head(&new->hnode, &json_cmd_assoc_hash[key]);
 }
 
 static json_t *seqnum_to_json(const uint32_t seqnum)
 {
-       const struct json_cmd_assoc *cur;
+       int key = seqnum % CMD_ASSOC_HSIZE;
+       struct json_cmd_assoc *cur;
+       struct hlist_node *n;
 
-       for (cur = json_cmd_list; cur; cur = cur->next) {
+
+       hlist_for_each_entry(cur, n, &json_cmd_assoc_hash[key], hnode) {
                if (cur->cmd->seqnum == seqnum)
                        return cur->json;
        }
+
        return NULL;
 }