IDF实现OTA下载新固件速度慢，要如何变快呢？

OTA的固件1.5MB不到, 运行OTA下载， 代码设计按照1%的递增显示进度，串口调试助手收到信息是每两秒才下载14KB。 平均每秒才7K。按照地址在网页浏览器下载， 每秒达到800多KB.
为什么这么慢呢？
    esp_err_t ota_finish_err = ESP_OK;    esp_http_client_config_t config = {        .url = OTA_FIRMWARE_UPGRADE_URI,        .cert_pem = NULL,  //(char *)server_cert_pem_start,    };        esp_https_ota_config_t ota_config = {        .http_config = &config,    };        esp_https_ota_handle_t https_ota_handle = NULL;    esp_err_t err = esp_https_ota_begin(&ota_config, &https_ota_handle);    if (err != ESP_OK) {        ESP_LOGE(TAG, "ESP HTTPS OTA Begin failed");        vTaskDelete(NULL);    }    esp_app_desc_t app_desc;    err = esp_https_ota_get_img_desc(https_ota_handle, &app_desc);    if (err != ESP_OK) {        ESP_LOGE(TAG, "esp_https_ota_read_img_desc failed");        goto ota_end;    }    err = validate_image_header(&app_desc);    if (err != ESP_OK) {        ESP_LOGE(TAG, "image header verification failed");        goto ota_end;    }    i = 0;    len = 0;    percent = 0;    while (1) {        //vTaskDelay(1000 / portTICK_PERIOD_MS);        err = esp_https_ota_perform(https_ota_handle);        if (err != ESP_ERR_HTTPS_OTA_IN_PROGRESS) {            break;        }        // esp_https_ota_perform returns after every read operation which gives user the ability to        // monitor the status of OTA upgrade by calling esp_https_ota_get_image_len_read, which gives length of image        // data read so far.        len = esp_https_ota_get_image_len_read(https_ota_handle);        if ((len - i) > 14336) {            percent++;            ESP_LOGE(TAG, "Image bytes read: %d, OTA : %d%%", len, percent);            i = len;        }    }