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FAT16 faster than FAT32? VDSP 5.0 Update 10.0

Question asked by dmann on Dec 9, 2011
Latest reply on Feb 8, 2012 by MartinK



Im working on the BF525 w/ _BF527_SDRAM_ISSUE_WORKAROUND undefined. I've made some of the changes you referred to in thread:


Moving the FSS Cache does not seems to provide a very significant improvement in write performance. I did notice that if the media is formatted in FAT16 vs FAT32 the performance is much better. Here's some example tests of media


Test: Write 512KB to media in using various fwrite() payloads. (I've tested adi_fss_ API to open/write/close with poorer performance, so chosen to use C I/O).



Generic 678MB - FAT161.41 MB/S0.80 MB/S1.48 MB/S1.49 MB/S1.51 MB/S0.84 MB/S0.85 MB/S
Generic 678MB - FAT320.51 MB/S0.74 MB/S0.74 MB/S0.75 MB/S0.75 MB/S0.54 MB/S0.54 MB/S



Also i've noticed huge improvements by undefining the _USE_BACKG_XFER define in the adi_usb.c ($Revision: 3459 $) for some media Example:


Generic - 2GB FAT16  _USE_BACKG_XFER undefined6.12 MB/S7.35 MB/S7.98 MB/S8.33 MB/S9.03 MB/S10.30 MB/S12.85 MB/S
Generic - 2GB FAT16  _USE_BACKG_XFER defined1.17 MB/S0.42 MB/S1.23 MB/S1.23 MB/S1.10 MB/S1.09 MB/S1.10 MB/S

but some slower media actually performs worse with this undefined. I was wondering if you had any advice on a procedure to determine the best settings for a particular connected USB device. Could you outline a generic procedure for using the information provided by the device to set up the fss/fsd for optimal settings? How might these settings change for a FAT16 device or FAT32 device with a certain number of clusters?


Should the cache be set to safe values like:



and then be changed one to media device has given back it's number of clusters? For example, if the media device returns that it has 64 clusters, should I reset the cache to:



If so, do i need to terminate the fss and re-init?


Right now my fss init looks like:


void InitFileSystem(void) 
    * Customized heaps for General, fat and atapi 'cache' type data
    int GeneralHeapID   = heap_lookup(1);
    //int CacheHeap = heap_lookup(2);
    * command table for the FAT driver
    static ADI_DEV_CMD_VALUE_PAIR ADI_FAT_ConfigTable [] = {
            { ADI_FAT_CMD_ENABLE_USAGE_STATS, (void*)true },
            //{ ADI_FSS_CMD_SET_CACHE_HEAP_ID,   (void*)0 },
            { ADI_DEV_CMD_END,                 NULL     },

    * definition structure for FAT driver - exported to application
    static ADI_FSS_DEVICE_DEF ADI_FAT_Def = {
        0,                                      /* N/A for FSD drivers                    */
        &ADI_FAT_EntryPoint,                    /* Entry Points for FAT Driver            */
        ADI_FAT_ConfigTable,                    /* Command Table to configure FAT driver  */
        NULL,                                   /* Critical region data                   */
        ADI_DEV_DIRECTION_BIDIRECTIONAL,        /* Direction (RW file system)             */

    * Configuration table to initialize the FSS
    ADI_FSS_CMD_VALUE_PAIR adi_fss_Config[] = {
        /* Personalized Memory Allocation Routines */
    #if defined(_DEBUG_ALLOC_)
        { ADI_FSS_CMD_SET_MALLOC_FUNC,      (void*)_adi_dbg_malloc },
        { ADI_FSS_CMD_SET_REALLOC_FUNC,     (void*)_adi_dbg_realloc },
        { ADI_FSS_CMD_SET_FREE_FUNC,        (void*)_adi_dbg_free },
        { ADI_FSS_CMD_SET_NUMBER_CACHE_BLOCKS,      (void*)2 },
        { ADI_FSS_CMD_SET_GENERAL_HEAP_ID,          (void*)GeneralHeapID },
        //{ ADI_FSS_CMD_SET_CACHE_HEAP_ID,          (void*)CacheHeap },
        { ADI_FSS_CMD_SET_MEDIA_CHANGE_CALLBACK, (void*)USBMediaDetectCallback },
        /* Add Media Devices - one command per type of Media Device Present */
           { ADI_FSS_CMD_ADD_DRIVER,           (void*)&ADI_USB_Def },
        //{ ADI_FSS_CMD_ADD_DRIVER,           (void*)&ADI_NAND_Def },
        /* Add File Systems - one command per type of File System Present */
        { ADI_FSS_CMD_ADD_DRIVER,           (void*)&ADI_FAT_Def },
        /* DMA and Device Manager Handles */
        { ADI_FSS_CMD_SET_DMA_MGR_HANDLE,   (void*)adi_dma_ManagerHandle },
        { ADI_FSS_CMD_SET_DEV_MGR_HANDLE,   (void*)adi_dev_ManagerHandle },
        { ADI_FSS_CMD_SET_DCB_MGR_HANDLE,   (void*)adi_dcb_QueueHandle },
        /* Command Table Terminator */
        { ADI_FSS_CMD_END, (void*)NULL }
    /* Initialize the file system service */
    adi_fss_Init ( adi_fss_Config );
    /* Add to CRT device table - which will make it the default */
    add_devtab_entry( &adi_fss_entry );