Threading +Model

In single core system, the active threads are executed in a time-sliced +fashion and appear to run in parallel. In a multi-core environment, multiple +threads can be executed in parallel and can also use time-sliced thread execution.

Single-threaded +codeThe applications designed with single threads will not have any +performance benefit by using multiple cores. The contention for CPU usage +may be reduced on multi-core hardware. The single threaded code should run +normally on multi-core hardware. Some code is more efficient +having single threads and some code performs better with multiple threads. It +is not recommended to modify a single-threaded application into multi-threaded +code until the existing code runs safely on multiple-core hardware. But new +applications can be designed to be multi-threaded to take advantage of the +SMP hardware.

Servers

Most +servers on Symbian platform are single threaded and are unlikely to need any +modification to migrate to a multi-core hardware. Some servers may need to +service multiple clients concurrently. One of the solutions to take advantage +of SMP hardware is to modify the servers to have multiple threads to service +the clients concurrently. The performance can also be improved by implementing +caching in the server.

Active scheduler

Active +schedulers are designed to be single threaded and the active objects never +run concurrently because there is no need for a lock in the data shared between +active objects. The active scheduler will only execute one active object at +a time. The existing code should run safely on multi-core hardware. If the +active objects need to use multiple cores then the code should be modified +to be multi-threaded and use locks when there is shared data between the threads.

User-side code

The +user-side applications that use Symbian platform Inter Process Communication +(IPC) functions like RThread::Rendezvous(), User::RequestComplete(), RSession::SendReceive() or Publish-Subscribe should run safely on multi-core hardware. If the user-side +code uses some proprietary IPC mechanism to communicate with other process, +that code may need to be modified to use Symbian IPC functions.

+The following table compares the advantages of single-threaded and multi-threaded +applications on an SMP hardware: + + + +Single-threaded applications +Multi-threaded applications + + + + + +Low CPU usage for schedulers +Parallel execution provides faster execution + + +Low memory overhead +Added control on power consumption + + +Low cache overhead +Servers that have to service multiple clients can run on different +CPUs + + + +