Settings: NVS: Add cache for nvs name lookup

Add cache for name id lookup.

Signed-off-by: Lingao Meng <menglingao@xiaomi.com>

subsys/settings/Kconfig

@@ -63,6 +63,24 @@ config SETTINGS_NVS
 	help
 	  Enables NVS storage support
 
+if SETTINGS_NVS
+
+config SETTINGS_NVS_NAME_CACHE
+	bool "NVS name lookup cache"
+	help
+	  Enable NVS name lookup cache, used to reduce the Settings name
+	  lookup time.
+
+config SETTINGS_NVS_NAME_CACHE_SIZE
+	int "NVS name lookup cache size"
+	default 128
+	range 1 65535
+	depends on SETTINGS_NVS_NAME_CACHE
+	help
+	  Number of entries in Settings NVS name cache.
+
+endif # SETTINGS_NVS
+
 config SETTINGS_CUSTOM
 	bool "CUSTOM"
 	help

subsys/settings/include/settings/settings_nvs.h

@@ -38,6 +38,14 @@ struct settings_nvs {
 	struct nvs_fs cf_nvs;
 	uint16_t last_name_id;
 	const struct device *flash_dev;
+#if CONFIG_SETTINGS_NVS_NAME_CACHE
+	struct {
+		uint16_t name_hash;
+		uint16_t name_id;
+	} cache[CONFIG_SETTINGS_NVS_NAME_CACHE_SIZE];
+
+	uint16_t cache_next;
+#endif
 };
 
 /* register nvs to be a source of settings */

subsys/settings/src/settings_nvs.c

@@ -10,6 +10,7 @@
 
 #include <zephyr/settings/settings.h>
 #include "settings/settings_nvs.h"
+#include <zephyr/sys/crc.h>
 #include "settings_priv.h"
 #include <zephyr/storage/flash_map.h>
 
@@ -72,6 +73,51 @@ int settings_nvs_dst(struct settings_nvs *cf)
 	return 0;
 }
 
+#if CONFIG_SETTINGS_NVS_NAME_CACHE
+static void settings_nvs_cache_add(struct settings_nvs *cf, const char *name,
+				   uint16_t name_id)
+{
+	uint16_t name_hash = crc16_ccitt(0xffff, name, strlen(name));
+
+	cf->cache[cf->cache_next].name_hash = name_hash;
+	cf->cache[cf->cache_next++].name_id = name_id;
+
+	cf->cache_next %= CONFIG_SETTINGS_NVS_NAME_CACHE_SIZE;
+}
+
+static uint16_t settings_nvs_cache_match(struct settings_nvs *cf, const char *name,
+					 char *rdname, size_t len)
+{
+	uint16_t name_hash = crc16_ccitt(0xffff, name, strlen(name));
+	int rc;
+
+	for (int i = 0; i < CONFIG_SETTINGS_NVS_NAME_CACHE_SIZE; i++) {
+		if (cf->cache[i].name_hash != name_hash) {
+			continue;
+		}
+
+		if (cf->cache[i].name_id <= NVS_NAMECNT_ID) {
+			continue;
+		}
+
+		rc = nvs_read(&cf->cf_nvs, cf->cache[i].name_id, rdname, len);
+		if (rc < 0) {
+			continue;
+		}
+
+		rdname[rc] = '\0';
+
+		if (strcmp(name, rdname)) {
+			continue;
+		}
+
+		return cf->cache[i].name_id;
+	}
+
+	return NVS_NAMECNT_ID;
+}
+#endif /* CONFIG_SETTINGS_NVS_NAME_CACHE */
+
 static int settings_nvs_load(struct settings_store *cs,
 			     const struct settings_load_arg *arg)
 {
@@ -125,6 +171,10 @@ static int settings_nvs_load(struct settings_store *cs,
 		read_fn_arg.fs = &cf->cf_nvs;
 		read_fn_arg.id = name_id + NVS_NAME_ID_OFFSET;
 
+#if CONFIG_SETTINGS_NVS_NAME_CACHE
+		settings_nvs_cache_add(cf, name, name_id);
+#endif
+
 		ret = settings_call_set_handler(
 			name, rc2,
 			settings_nvs_read_fn, &read_fn_arg,
@@ -152,6 +202,15 @@ static int settings_nvs_save(struct settings_store *cs, const char *name,
 	/* Find out if we are doing a delete */
 	delete = ((value == NULL) || (val_len == 0));
 
+#if CONFIG_SETTINGS_NVS_NAME_CACHE
+	name_id = settings_nvs_cache_match(cf, name, rdname, sizeof(rdname));
+	if (name_id != NVS_NAMECNT_ID) {
+		write_name_id = name_id;
+		write_name = false;
+		goto found;
+	}
+#endif
+
 	name_id = cf->last_name_id + 1;
 	write_name_id = cf->last_name_id + 1;
 	write_name = true;
@@ -178,7 +237,24 @@ static int settings_nvs_save(struct settings_store *cs, const char *name,
 			continue;
 		}
 
-		if ((delete) && (name_id == cf->last_name_id)) {
+		if (!delete) {
+#if CONFIG_SETTINGS_NVS_NAME_CACHE
+			settings_nvs_cache_add(cf, name, name_id);
+#endif
+			write_name_id = name_id;
+			write_name = false;
+		}
+
+		goto found;
+	}
+
+found:
+	if (delete) {
+		if (name_id == NVS_NAMECNT_ID) {
+			return 0;
+		}
+
+		if (name_id == cf->last_name_id) {
 			cf->last_name_id--;
 			rc = nvs_write(&cf->cf_nvs, NVS_NAMECNT_ID,
 				       &cf->last_name_id, sizeof(uint16_t));
@@ -190,26 +266,17 @@ static int settings_nvs_save(struct settings_store *cs, const char *name,
 			}
 		}
 
-		if (delete) {
+		rc = nvs_delete(&cf->cf_nvs, name_id);
-			rc = nvs_delete(&cf->cf_nvs, name_id);
 
-			if (rc >= 0) {
+		if (rc >= 0) {
-				rc = nvs_delete(&cf->cf_nvs, name_id +
+			rc = nvs_delete(&cf->cf_nvs, name_id +
 					NVS_NAME_ID_OFFSET);
-			}
-
-			if (rc < 0) {
-				return rc;
-			}
-
-			return 0;
 		}
-		write_name_id = name_id;
-		write_name = false;
-		break;
-	}
 
-	if (delete) {
+		if (rc < 0) {
+			return rc;
+		}
+
 		return 0;
 	}