Re: Change TCG cache size?

[Kenneth Adam Miller]

Well, maybe I'm understanding that wrong. I am talking the cache that the tcg keeps of translated code. If I got that variable wrong then please let me know. But I want to make sure that that is large enough to keep from having to run TCG again. How can I do that?

On Wed, Sep 22, 2021, 6:54 AM Alex Bennée <alex.bennee@linaro.org> wrote:

Kenneth Adam Miller <kennethadammiller@gmail.com> writes:

> Hello all,
>
> I just want to ask this one question: if I change the qemu tcg cache
> size (TB_JMP_CACHE_SIZE), will that force any errors at run time?

Hopefully not - for both user-mode and softmmu we take some care to
ensure tb_jmp_cache_hash_func and tb_jmp_cache_hash_page return
appropriately masked values for the table lookup.

What has not been done since Emilio's work in 6f1653180f (tb-hash:
improve tb_jmp_cache hash function in user mode) is a deeper look at the
hit rate and bounce rate of the softmmu jump table hashing. Any
suggested changes will need some benchmarking to show what difference it
makes.

--
Alex Bennée