We did the following tests:* About Linux side, two load conditions have been considered:** idle** Google stressapptest (SAT for short) <ref name="SAT">https://code.google.com/p/stressapptest/"</ref>, stressing running to stress SDRAM memory and SD I/O.* About RTOS side:** idle** memory intensive task; two subcases, in turn, have been considered to evaluate the impact of the L2 cache unavailability.

The RTOS memory task access an array in main memory of two different sizesizes:

* the larger is 4 times the L1 size(128KiB)

* program programs PS TTC timer as freerun, triggering an interrupt on overflow* inside the overflow ISR it read the TTC counteris read: this counter reports the number of ticks passed elapsed between the event (overflow) and the handler itself, in other words our the interrupt latency* after a while the TTC is reprogrammed and interrupt is enabled again, to trigger another event* those ''latency countercounters'' are collected into an array* the Linux-side application, by default after 10 seconds, stop stops the RTOS task which sends the array data over RPMSRPMsg* the Linux-side application collect collects the data and display the mininum, maximum and average latency measured

[[FileThe following conclusions can be drawn from the test results:TBD.png|thumb|left|100px]]<br clear=all>===Isolation vs performances===This work confirmed the need to find a trade* Real-off between two requirements that often push in opposite directions: isolation and performances. On one hand isolation should be pushed to the maximum possible extent to preserve the integrity timeness of W1 worldrealm is preserved in any condition, since Linux activity on CPU/memory/SD virtually has no influence on RTOS latency. On the other hand, overall systems performances have not to be affected so much that the product gets unusable* Moderate RTOS activity has no impact on latency. Generally speaking* As expected, strong isolation negatively impacts performancesin case intensive memory activity is performed on RTOS side, so finding the optimal balancing is not trivial. A "one size fits all" solution does not exist and system designer is responsible to choose which direction this knob has to be moved. This analysis naturally has to take into account application-specific requirementsdata/instruction cache misses increase significantly resulting in higher latency.

Future work will first focus on an additional feature that has not been included in the requirement list but that is undoubtedly useful in several applications. We are referring to the possibility of performing a complete reboot of the GPOS under the control of the RTOS, while this keeps operating normally. For instance this can be exploited when the RTOS needs to work as software watchdog for W2 activity: in case no activity is detected for a certain period of time, GPOS can be shutdown and rebooted.