Re: [PATCH] icount: improve exec nocache usage

[Paolo Bonzini <pbonzini@redhat.com>]

On 08/12/20 10:10, Pavel Dovgalyuk wrote:
> cpu-exec tries to execute TB without caching when current
> icount budget is over. But sometimes refilled budget is big
> enough to try executing cached blocks.
> This patch checks that instruction budget is big enough
> for next block execution instead of just running cpu_exec_nocache.
> It halves the number of calls of cpu_exec_nocache function
> during tested OS boot scenario.
> 
> Signed-off-by: Pavel Dovgalyuk <pavel.dovgalyuk@ispras.ru>
> ---
>   accel/tcg/cpu-exec.c |    2 +-
>   1 file changed, 1 insertion(+), 1 deletion(-)
> 
> diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
> index 58aea605d8..251b340fb9 100644
> --- a/accel/tcg/cpu-exec.c
> +++ b/accel/tcg/cpu-exec.c
> @@ -685,7 +685,7 @@ static inline void cpu_loop_exec_tb(CPUState *cpu, TranslationBlock *tb,
>       insns_left = MIN(0xffff, cpu->icount_budget);
>       cpu_neg(cpu)->icount_decr.u16.low = insns_left;
>       cpu->icount_extra = cpu->icount_budget - insns_left;
> -    if (!cpu->icount_extra) {
> +    if (!cpu->icount_extra && insns_left < tb->icount) {
>           /* Execute any remaining instructions, then let the main loop
>            * handle the next event.
>            */
> 

Queued, thanks.

Paolo