Media Processing and Load Supervision
Unlike the MGU boards, there are no dedicated DSPs for the media processing. Instead, all media processing is done by the CPU(s) on the machine it runs on. Thus, any general processing on the server might affect active media processing causing bad speech. To mitigate media issues, the media processing is running at a high priority with real-time scheduling and the Media Server prevents the server from being too high loaded by internal CPU load supervision.
The MX-ONE Media Server supports multi-core CPUs and will adapt the number of media processing threads (referred to as clock threads) to the number of available CPU cores on the machine, which means that higher capacity is reached for servers with many cores, but also means more memory is required.
In a virtualized environment, the Media Server will only “see” the number of cores configured for the virtual machine it runs on.
The MX-ONE Media Server checks CPU load periodically to set an overload condition if load is above a “high watermark”. If an overload condition is set, starting new media resources is rejected by Media Server. Service Node will ultimately pause requests to this Media Server until overload has ceased. The overload condition will not cease until Media Server has checked load is below a “low watermark”. CPU load is calculated and checked each 2 second and “high watermark” is at 80% CPU load and “low watermark” is at 75% CPU load. When high watermark is passed, it will be logged as a warning (WARN) message, and when ceased as an informal (INFO) message.
The CPU intense short operations on the server might trigger overload situations that can cause these warnings but is generally not a problem. Upgrade and backup operations are typical Service Node operations that can cause this, but there are also Linux operations and periodical tasks like the security check (secheck) that can cause intermediate overload (see Administrator User’s Guide for more information about (secheck). For these reasons, Stand-alone installation is preferred over Co-located installation, and CPU intense tasks on Media Server should be considered for scheduling at low traffic time.
As a general recommendation, a server with Media Server installation should have at least 2 CPU cores or more. This is recommended for “Co-located” as well as for “Stand-alone” deployment (See section Installation). In a virtualized environment it is important to consider the number of virtual CPUs configured in the Virtual Machine that runs Media Server.