Re: [RFC PATCH 2/6] accel/tcg: Avoid uncessary call overhead from qemu_plugin_vcpu_mem_cb

[Richard Henderson]

On 2/15/24 09:28, Max Chou wrote:
> If there are not any QEMU plugin memory callback functions, checking
> before calling the qemu_plugin_vcpu_mem_cb function can reduce the
> function call overhead.
>
> Signed-off-by: Max Chou <max.chou@sifive.com>
> ---
>   accel/tcg/ldst_common.c.inc | 40 +++++++++++++++++++++++++++----------
>   1 file changed, 30 insertions(+), 10 deletions(-)
>
> diff --git a/accel/tcg/ldst_common.c.inc b/accel/tcg/ldst_common.c.inc
> index c82048e377e..bf24986c562 100644
> --- a/accel/tcg/ldst_common.c.inc
> +++ b/accel/tcg/ldst_common.c.inc
> @@ -134,7 +134,9 @@ uint8_t cpu_ldb_mmu(CPUArchState *env, abi_ptr addr, 
> MemOpIdx oi, uintptr_t ra)
>   
>       tcg_debug_assert((get_memop(oi) & MO_SIZE) == MO_UB);
>       ret = do_ld1_mmu(env_cpu(env), addr, oi, ra, MMU_DATA_LOAD);
> -    plugin_load_cb(env, addr, oi);
> +    if (cpu_plugin_mem_cbs_enabled(env_cpu(env))) {
> +        plugin_load_cb(env, addr, oi);
> +    }
>       return ret;
>   }

Rather than repeating N times, modify plugin_load_cb and plugin_store_cb just above to 
avoid the call to cpu_plugin_mem_cbs_enabled().  I expect the compiler is inlining those 
functions already.


r~