c# - should I just set SuppressUnmanagedCodeSecurity for maximum performance?

Question

Am I correct that if I need maximum performance, and I have trusted library I should just set SuppressUnmanagedCodeSecurity attribute to all Dll imports I have?

I.e. convert such import:

    [DllImport("srl.dll", CharSet = CharSet.Ansi)]
    private static extern string ErrorMsg(int ErrCode);

to such import:

    [DllImport("srl.dll", CharSet = CharSet.Ansi), SuppressUnmanagedCodeSecurity]
    private static extern string ErrorMsg(int ErrCode);

everywhere.

Are there any reasons not to set SuppressUnmanagedCodeSecurity?