I have posted an issue I am having with the use of mbedTLS with ESP8266 SDK (it is freeRTOS based), I have posted my explanation in the link below, then their support asked me to send new questions to this email.

If you have any doubt regarding my tests, or if you want I make more different tests, please don't hesitate do ask me.

https://forums.mbed.com/t/mbedtls-on-esp8266-sdk-memory-issue/7913 

Regards.