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nvs: Check if an item is modified before writing out an identical copy

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This prevents wear and tear on the flash, and it also is faster in some
cases since the read-out of flash is a cheaper operation than the erasure
of flash.  Some library modules (such as the esp_wifi) write out to NVS
upon every initialization without checking first that the existing value
is the same, and this speeds up initialization of modules that make
these design choices and moves it into a centralized place.

The comparison functions are based on the read-out functions of the same
name, and changes out the memcpy(...) operations for memcmp(...)
operations.

Signed-off-by: Tim Nordell <tim.nordell@nimbelink.com>
This commit is contained in:
Tim Nordell
2019-04-15 14:06:57 -05:00
parent ba1ff1692b
commit c3fa2497b9
6 changed files with 176 additions and 5 deletions
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62
components/nvs_flash/test_nvs_host/test_nvs.cpp
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@@ -376,8 +376,8 @@ TEST_CASE("storage doesn't add duplicates within one page", "[nvs]")
emu.setBounds(4, 8);
CHECK(storage.init(4, 4) == ESP_OK);
int bar = 0;
CHECK(storage.writeItem(1, "bar", bar) == ESP_OK);
CHECK(storage.writeItem(1, "bar", bar) == ESP_OK);
CHECK(storage.writeItem(1, "bar", ++bar) == ESP_OK);
CHECK(storage.writeItem(1, "bar", ++bar) == ESP_OK);
Page page;
page.load(4);
@@ -404,11 +404,11 @@ TEST_CASE("storage doesn't add duplicates within multiple pages", "[nvs]")
emu.setBounds(4, 8);
CHECK(storage.init(4, 4) == ESP_OK);
int bar = 0;
CHECK(storage.writeItem(1, "bar", bar) == ESP_OK);
CHECK(storage.writeItem(1, "bar", ++bar) == ESP_OK);
for (size_t i = 0; i < Page::ENTRY_COUNT; ++i) {
CHECK(storage.writeItem(1, "foo", static_cast<int>(bar)) == ESP_OK);
CHECK(storage.writeItem(1, "foo", static_cast<int>(++bar)) == ESP_OK);
}
CHECK(storage.writeItem(1, "bar", bar) == ESP_OK);
CHECK(storage.writeItem(1, "bar", ++bar) == ESP_OK);
Page page;
page.load(4);
@@ -750,6 +750,58 @@ TEST_CASE("wifi test", "[nvs]")
}
TEST_CASE("writing the identical content does not write or erase", "[nvs]")
{
SpiFlashEmulator emu(20);
const uint32_t NVS_FLASH_SECTOR = 5;
const uint32_t NVS_FLASH_SECTOR_COUNT_MIN = 10;
emu.setBounds(NVS_FLASH_SECTOR, NVS_FLASH_SECTOR + NVS_FLASH_SECTOR_COUNT_MIN);
TEST_ESP_OK(nvs_flash_init_custom(NVS_DEFAULT_PART_NAME, NVS_FLASH_SECTOR, NVS_FLASH_SECTOR_COUNT_MIN));
nvs_handle misc_handle;
TEST_ESP_OK(nvs_open("test", NVS_READWRITE, &misc_handle));
// Test writing a u8 twice, then changing it
nvs_set_u8(misc_handle, "test_u8", 8);
emu.clearStats();
nvs_set_u8(misc_handle, "test_u8", 8);
CHECK(emu.getWriteOps() == 0);
CHECK(emu.getEraseOps() == 0);
CHECK(emu.getReadOps() != 0);
emu.clearStats();
nvs_set_u8(misc_handle, "test_u8", 9);
CHECK(emu.getWriteOps() != 0);
CHECK(emu.getReadOps() != 0);
// Test writing a string twice, then changing it
static const char *test[2] = {"Hello world.", "Hello world!"};
nvs_set_str(misc_handle, "test_str", test[0]);
emu.clearStats();
nvs_set_str(misc_handle, "test_str", test[0]);
CHECK(emu.getWriteOps() == 0);
CHECK(emu.getEraseOps() == 0);
CHECK(emu.getReadOps() != 0);
emu.clearStats();
nvs_set_str(misc_handle, "test_str", test[1]);
CHECK(emu.getWriteOps() != 0);
CHECK(emu.getReadOps() != 0);
// Test writing a multi-page blob, then changing it
uint8_t blob[Page::CHUNK_MAX_SIZE * 3] = {0};
memset(blob, 1, sizeof(blob));
nvs_set_blob(misc_handle, "test_blob", blob, sizeof(blob));
emu.clearStats();
nvs_set_blob(misc_handle, "test_blob", blob, sizeof(blob));
CHECK(emu.getWriteOps() == 0);
CHECK(emu.getEraseOps() == 0);
CHECK(emu.getReadOps() != 0);
blob[sizeof(blob) - 1]++;
emu.clearStats();
nvs_set_blob(misc_handle, "test_blob", blob, sizeof(blob));
CHECK(emu.getWriteOps() != 0);
CHECK(emu.getReadOps() != 0);
}
TEST_CASE("can init storage from flash with random contents", "[nvs]")
{