Does Unicorn still keep and use the cache after ending execution of uc_emu_start ?

Context:

I'm emulating a type of OS and have to stop each 20000 ticks to reschedule emulated threads. It's something of this:

     while (!shutdown) {
         uc_emu_start(engine, pc, 1ULL << 63, 0, 20000);
         do_kernel_reschedule();
     }

If I try to run this without instructions limit, and do reschedule in code hook, it's super fast. But if I do like above, the performance drops are noticeable, especially when the emulated system enters a big loop.
It's not my reschedule that's slow, because there is another JIT backend I use, that although slower than Unicorn in general, but it keeps the cache and suprass Unicorn in loop situation.
So does Unicorn still keep cache after uc_emu_start done?

TLDR: Unicorn is slow when restarting continously. I want to ask if Unicorn stills keep cache after uc_emu_start done.

I'm happy to provide more information. Thanks.

Note: The build I'm using is release build on the web, but this question still relevant to master branch on github.

I think I found the evil line:

unicorn/qemu/cpu-exec.c

Lines 279 to 282 in 19ffa83

    
           // Unicorn: flush JIT cache to because emulation might stop in 
        
           // the middle of translation, thus generate incomplete code. 
        
           // TODO: optimize this for better performance 
        
           tb_flush(env);

Waiting for an optimization :)

	// Unicorn: flush JIT cache to because emulation might stop in
	// the middle of translation, thus generate incomplete code.
	// TODO: optimize this for better performance
	tb_flush(env);