utils/cache_gc: comments and cleanup in kr_cache_gc()

diff --git a/utils/cache_gc/kr_cache_gc.c b/utils/cache_gc/kr_cache_gc.c
index 1c0e376c439692af38ee64b142024ac8fb1ca80b..271fdb77b7e6d38d09efca4ee42054398547e552 100644 (file)
--- a/utils/cache_gc/kr_cache_gc.c
+++ b/utils/cache_gc/kr_cache_gc.c
@@ -161,9 +161,12 @@ void kr_cache_gc_free_state(kr_cache_gc_state_t **state)
 
 int kr_cache_gc(kr_cache_gc_cfg_t *cfg, kr_cache_gc_state_t **state)
 {
+       // The whole function works in four "big phases":
+       //// 1. find out whether we should even do analysis and deletion.
        assert(cfg && state);
        int ret;
-       if (!*state) { // Cache not open -> do that.
+       // Ensure that we have open and "healthy" cache.
+       if (!*state) {
                *state = calloc(1, sizeof(**state));
                if (!*state) {
                        return KNOT_ENOMEM;
@@ -181,17 +184,7 @@ int kr_cache_gc(kr_cache_gc_cfg_t *cfg, kr_cache_gc_state_t **state)
        }
        knot_db_t *const db = (*state)->db; // frequently used shortcut
 
-       const struct kr_cdb_api *cache_api = kr_cdb_lmdb();
-       const double db_usage = cache_api->usage_percent(db);
-#if 0                          // Probably not worth it, better reduce the risk by checking more often.
-       if (db_usage > 90.0) {
-               free(*libknot_db);
-               kr_cache_close(kres_db);
-               cache_size += cache_size / 10;
-               opts.maxsize = cache_size;
-               goto open_kr_cache;
-       }
-#endif
+       const double db_usage = kr_cdb_lmdb()->usage_percent(db);
        const bool large_usage = db_usage >= cfg->cache_max_usage;
        if (cfg->dry_run || large_usage) {      // don't print this on every size check
                printf("Usage: %.2lf%%\n", db_usage);
@@ -200,6 +193,8 @@ int kr_cache_gc(kr_cache_gc_cfg_t *cfg, kr_cache_gc_state_t **state)
                return KNOT_EOK;
        }
 
+       //// 2. classify all cache items into categories
+       //      and compute which categories to delete.
        gc_timer_t timer_analyze = { 0 }, timer_choose = { 0 }, timer_delete =
            { 0 }, timer_rw_txn = { 0 };
 
@@ -241,6 +236,7 @@ int kr_cache_gc(kr_cache_gc_cfg_t *cfg, kr_cache_gc_state_t **state)
        printf("Cache analyzed in %.2lf secs, %zu records, limit category is %d.\n",
               gc_timer_end(&timer_analyze), cats.records, limit_category);
 
+       //// 3. pass whole cache again to collect a list of keys that should be deleted.
        gc_timer_start(&timer_choose);
        ctx_delete_categories_t to_del = { 0 };
        to_del.cfg_temp_keys_space = cfg->temp_keys_space;
@@ -256,6 +252,7 @@ int kr_cache_gc(kr_cache_gc_cfg_t *cfg, kr_cache_gc_state_t **state)
             to_del.to_delete.size, ((double)to_del.used_space / 1048576.0),
             to_del.oversize_records);
 
+       //// 4. execute the planned deletions.
        const knot_db_api_t *api = knot_db_lmdb_api();
        knot_db_txn_t txn = { 0 };
        size_t deleted_records = 0, already_gone = 0, rw_txn_count = 0;