我有一个简单的Azure函数，它在服务总线队列上触发，从存储帐户下载数据，执行一些简单的逻辑，并将消息发送到另一个服务总线队列。函数正在使用连接字符串（共享访问密钥）进行身份验证。为了遵循最佳实践和建议，我将身份验证方法更改为托管身份。在此更改之后，我注意到性能显著下降= >从存储帐户下载数据并将消息发送到队列所需时间延长了2.5倍。
作为一个例子，我创建了两个简单的函数。两者都是从服务总线队列触发，从blob下载内容，唯一的区别是身份验证方法。第一个的运行时间显著小于第二个。

[FunctionName("TestFuncWithConnString")]
    public async Task Run(
        [ServiceBusTrigger("testconstring", Connection = "ServiceBusConnectionString")] ServiceBusReceivedMessage message,
        ServiceBusMessageActions messageActions)
    {

        var storageConnectionString = _configuration.GetConnectionString("StorageConnectionString");
        var blobContainerClient = new BlobContainerClient(storageConnectionString, "containerName");   
        var blobClient = blobContainerClient.GetBlobClient("XXX");
        var blobMessage = await blobClient.DownloadAsync();

        await messageActions.CompleteMessageAsync(message);
    }

    [FunctionName("TestFuncWithManagedIdentity")]
    public async Task Run(
        [ServiceBusTrigger("testmanagedidentity ", Connection = "SBNamespaceFQName")] ServiceBusReceivedMessage message,
        ServiceBusMessageActions messageActions)
    {

        var storageConnectionString = new Uri($"https://{StorageAccount}.blob.core.windows.net/");

        var blobServiceClient = new BlobServiceClient(storageConnectionString, new DefaultAzureCredential());
        var blobContainerClient = blobServiceClient.GetBlobContainerClient("containerName");
        var blobClient = blobContainerClient.GetBlobClient("XXX");
        var blobMessage = await blobClient.DownloadAsync();

        await messageActions.CompleteMessageAsync(message);
    }

有谁知道这里出了什么问题吗？