HiperSockets Enhancement for zIIP Exploitation

interrupt. This enhancement is transparent to the operating system in the receiving LPAR. HiperSockets Multiple Write Facility, with fewer I/O interrupts, is designed to reduce CPU utilization of the sending and receiving LPAR.

The HiperSockets Multiple Write solution moves multiple output data buffers in one write operation.

If the function is disabled then one output data buffer is moved in one write operation. This is also how HiperSockets functioned in the past.

If the function is enabled then multiple output data buf- fers are moved in one write operation. This reduces CPU utilization related to large outbound messages. When enabled, HiperSockets Multiple Write will be used anytime a message spans an IQD frame requiring multiple output data buffers (SBALs) to transfer the message. Spanning multiple output data buffers can be affected by a number of factors including:

•IQD frame size

•Application socket send size

•TCP send size

•MTU size

The HiperSockets Multiple Write Facility is supported in the z/OS environment. For a complete description of the System z10 connectivity capabilities refer to IBM System z Connectivity Handbook, SG24-5444.

HiperSockets Multiple Write Facility and zIIP enablement is described as “zIIP-Assisted HiperSockets for large mes- sages.” zIIP-Assisted HiperSockets can help make highly secure, available, virtual HiperSockets networking a more attractive option. z/OS application workloads based on XML, HTTP, SOAP, Java, etc., as well as traditional ﬁ le transfer, can beneﬁ t from zIIP enablement by helping to lower general purpose processor utilization for such TCP/ IP trafﬁ c.

Only outbound z/OS TCP/IP large messages which origi- nate within a z/OS host are eligible for HiperSockets zIIP- Assisted processing. Other types of network trafﬁ c such as IP forwarding, Sysplex Distributor, inbound processing, small messages, or other non TCP/IP network protocols are not eligible for zIIP-Assisted HiperSockets. When the workload is eligible, then the TCP/IP HiperSockets device driver layer (write) processing is redirected to a zIIP, which will unblock the sending application. zIIP Assisted HiperSockets for large messages is available with z/OS V1.10 with PTF and System z10 only. This feature is unsup- ported if z/OS is running as a guest in a z/VM environment and is supported for large outbound messages only.

To estimate potential ofﬂ oad, use PROJECTCPU for current and existing workloads. This is accurate and very simple, but you have to be on z/OS 1.10 with the enabling PTFs AND System z10 server AND you need to be performing HiperSockets Multiple Write workload already on z/OS.