I measured time for context switching on logic state analizer and I get 10us. Please tell me whether it isn’t too long for this microcontroller? I need high frequency tick to "very real-time" application, so when I set up TICK_RATE_HZ too high, time for my tasks is very short. I thought that machine like STR912 should switch context much faster. It is possible to decrease time for context switch? Regards

If you have a high precision timing requirement then you can use the FIQ interrupt so the FreeRTOS does not have an effect on your timing.  You cannot call API function from that though.  Keep in mind that the flash interface makes the original STR9 slower than some ARM7 devices.  I think some better versions are out now.