QDIO interface isolation is supported on all OSA-Express features on z15. The supported  operating systems are listed in Table 7-8 on page 267 and Table 7-9 on page 269. QDIO optimized latency mode (OLM) can help improve performance for applications that  feature a critical requirement to minimize response times for inbound and outbound data. OLM optimizes the interrupt processing in the following manner: The supported operating systems are listed in Table 7-8 on page 267. QDIO Diagnostic Synchronization enables system programmers and network administrators  to coordinate and simultaneously capture software and hardware traces. It allows z/OS to  signal OSA-Express features (by using a diagnostic assist function) to stop traces and  capture the current trace records. QDIO Diagnostic Synchronization is supported by the OSA-Express features on z15 when in  QDIO mode (CHPID type OSD). The supported operating systems are listed in Table 7-8 on  page 267. Linux on Z and z/VM work together to provide performance improvements by using  extensions to the QDIO architecture. First added to z/Architecture with HiperSockets, adapter  interruptions provide an efficient, high-performance technique for I/O interruptions to reduce  path lengths and processor usage. These reductions are in the host operating system and the  adapter (supported OSA-Express cards when CHPID type OSD is used). In extending the use of adapter interruptions to OSD (QDIO) channels, the processor  utilization to handle a traditional I/O interruption is reduced. This configuration benefits  OSA-Express TCP/IP support in z/VM, z/VSE, and Linux on Z. The supported operating  systems are listed in Table 7-8 on page 267 and Table 7-9 on page 269. OSA-Express3 introduced inbound workload queuing (IWQ), which creates multiple input  queues and allows OSA to differentiate workloads “off the wire.” It then assigns work to a  specific input queue (per device) to z/OS. Each input queue is a unique type of workload, and has unique service and processing  requirements. The IWQ function allows z/OS to preassign the appropriate processing  resources for each input queue. This approach allows multiple concurrent z/OS processing  threads to process each unique input queue (workload), which avoids traditional resource  contention.  IWQ reduces the conventional z/OS processing that is required to identify and separate  unique workloads. This advantage results in improved overall system performance and  scalability. Inbound workload queuing (IWQ) for OSA Adapter interruptions for QDIO QDIO Diagnostic Synchronization QDIO optimized latency mode GLYPH<SM590000> For inbound processing, the TCP/IP stack looks more frequently for available data to  process. This process ensures that any new data is read from the OSA-Express features  without needing more program controlled interrupts (PCIs). GLYPH<SM590000> For outbound processing, the OSA-Express cards also look more frequently for available  data to process from the TCP/IP stack. Therefore, the process does not require a Signal  Adapter (SIGA) instruction to determine whether more data is available. 312  IBM z15 (8561) Technical Guide