Overview

The using of use of SocketOpPrioritysession  session parameter is based on a variety of ways of doing network I/O (input/output):

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Dedicated threads allow lower response time , while using a pool provides higher throughput. So the optimal combination of "how to do I/O" and "what performs I/O (current thread/thread pool/dedicated thread)" choices depends on the application.

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• EVEN (default) - share worker thread among all session sessions in the Engine;
• AGGRESSIVE_SEND - use dedicated per session thread to send outgoing messages;
• AGGRESSIVE_RECEIVE - use dedicated per session thread to receive incoming messages;
• AGGRESSIVE_SEND_AND_RECEIVE - use dedicated per session threads to send and receive messages;

• DIRECT_SEND - use the current thread for sending, if this would block, performs as "EVEN".

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It's recommended to use EVEN when there are many concurrent sessions ("many" means much more that than the count of cores used), i.e. application demands a high throughput rather than a low response time. Allocating dedicated per session threads is not an option in such cases, so using a pool makes sense.

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Tries to send the message from the current thread, if that fails (would block) delegates sending to a dedicated per session thread. Uses a combination of busy polling and readiness notifications. Intended for applications which that need low response time (e.g. to send an order as soon as possible).

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Use a dedicated per session thread handles to handle receiving. It uses I/O with busy polling and switches to readiness notifications if no data has been received during the a certain configurable time interval. Intended for applications which that need low response time (e.g. to receive and react as soon as possible).

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It's recommended to use DIRECT_SEND when there are many concurrent sessions ("many" means much more than the count of cores used), but on the other hand, an application needs a low(er) response time rather than a high throughput.