a35bb6608d
Issue: When the setting nvs cache is disabled and `settings_nvs_save` is called, the function reads all stored setting name entries from NVS until either finds the desired setting name entry or reaches the last stored setting name entry. With the settings nvs cache enabled, `settings_nvs_save` runs through the cached setting name entries first. If the cached entry matches with the desired one, it immediately writes the new setting value to NVS that corresponds to the cached setting name entry. However, if the setting name entry is not found in the cache (which is the case for a new entry), `settings_nvs_save` reads all stored setting name entries from NVS again. This means that even if the number of stored entries in the settings is less than the cache size, for each new setting entry to be stored `settings_nvs_save` will first run through the cache, then read all stored setting name entries from NVS and only then will pick the next free name id for this new setting name entry and will finally store the new setting entry. This makes the cache ineffiсient for every new entry to be stored even when the cache size is always able to keep all setting entries that will be stored in NVS. Use-case: In the Bluetooth mesh there is a Replay Protection List which keeps sequence numbers of all nodes it received messages from. The RPL is stored persistently in NVS. The setting name entry is the source address of the node and the setting value entry is the sequence number. The common use case is when RPL is quite big (for example, 255 entries). With the current settings nvs cache implementation, every time the node stores a new RPL entry in settings (which is the first received message from a particular source address), `settings_nvs_save` will always check the cache first, then also read all stored entries in NVS and only then will figure out that this is a new entry. With every new RPL entry to be stored this search time increases. This behavior results in much worse performance in comparison with when the corresponding entry was already stored. E.g. on nRF52840, with bare minimal mesh stack configuration, when the cache is bigger than number of stored entries or close to it, storing of 255 RPL entries takes ~25 seconds. The time of subsequent store of 255 RPL entires is ~2 seconds with the cache. Solution: This commit improves the behavior of the first write by bypassing the reading from NVS if the following conditions are met: 1. `settings_nvs_load` was called, 2. the cache was not overflowed (bigger than the number of stored entries). As long as these 2 conditiones are met, it is safe to skip reading from NVS, pick the next free name id and write the value immediately. Signed-off-by: Pavel Vasilyev <pavel.vasilyev@nordicsemi.no>
68 lines
1.6 KiB
C
68 lines
1.6 KiB
C
/*
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* Copyright (c) 2019 Laczen
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* Copyright (c) 2019 Nordic Semiconductor ASA
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*
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* SPDX-License-Identifier: Apache-2.0
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*/
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#ifndef __SETTINGS_NVS_H_
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#define __SETTINGS_NVS_H_
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#include <zephyr/fs/nvs.h>
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#include <zephyr/settings/settings.h>
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#ifdef __cplusplus
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extern "C" {
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#endif
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/* In the NVS backend, each setting is stored in two NVS entries:
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* 1. setting's name
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* 2. setting's value
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*
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* The NVS entry ID for the setting's value is determined implicitly based on
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* the ID of the NVS entry for the setting's name, once that is found. The
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* difference between name and value ID is constant and equal to
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* NVS_NAME_ID_OFFSET.
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*
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* Setting's name entries start from NVS_NAMECNT_ID + 1. The entry at
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* NVS_NAMECNT_ID is used to store the largest name ID in use.
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*
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* Deleted records will not be found, only the last record will be
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* read.
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*/
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#define NVS_NAMECNT_ID 0x8000
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#define NVS_NAME_ID_OFFSET 0x4000
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struct settings_nvs {
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struct settings_store cf_store;
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struct nvs_fs cf_nvs;
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uint16_t last_name_id;
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const struct device *flash_dev;
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#if CONFIG_SETTINGS_NVS_NAME_CACHE
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struct {
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uint16_t name_hash;
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uint16_t name_id;
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} cache[CONFIG_SETTINGS_NVS_NAME_CACHE_SIZE];
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uint16_t cache_next;
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uint16_t cache_total;
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bool loaded;
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#endif
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};
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/* register nvs to be a source of settings */
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int settings_nvs_src(struct settings_nvs *cf);
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/* register nvs to be the destination of settings */
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int settings_nvs_dst(struct settings_nvs *cf);
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/* Initialize a nvs backend. */
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int settings_nvs_backend_init(struct settings_nvs *cf);
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#ifdef __cplusplus
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}
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#endif
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#endif /* __SETTINGS_NVS_H_ */
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