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

[Daniel Henrique Barboza]

On 2/15/24 16:28, 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>
> ---

This was in my TODO list for some time. Thanks for looking it up.

Can't we avoid all callbacks, not just qemu_plugin_vcpu_mem_cb, if there's no
plugin loaded? The performance increase when building with --disable-plugins
shouldn't be a thing - if the user isn't using plug-ins it should have a
penalty to it.

Thanks,

Daniel

>   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;
>   }
>   
> @@ -145,7 +147,9 @@ uint16_t cpu_ldw_mmu(CPUArchState *env, abi_ptr addr,
>   
>       tcg_debug_assert((get_memop(oi) & MO_SIZE) == MO_16);
>       ret = do_ld2_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;
>   }
>   
> @@ -156,7 +160,9 @@ uint32_t cpu_ldl_mmu(CPUArchState *env, abi_ptr addr,
>   
>       tcg_debug_assert((get_memop(oi) & MO_SIZE) == MO_32);
>       ret = do_ld4_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;
>   }
>   
> @@ -167,7 +173,9 @@ uint64_t cpu_ldq_mmu(CPUArchState *env, abi_ptr addr,
>   
>       tcg_debug_assert((get_memop(oi) & MO_SIZE) == MO_64);
>       ret = do_ld8_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;
>   }
>   
> @@ -178,7 +186,9 @@ Int128 cpu_ld16_mmu(CPUArchState *env, abi_ptr addr,
>   
>       tcg_debug_assert((get_memop(oi) & MO_SIZE) == MO_128);
>       ret = do_ld16_mmu(env_cpu(env), addr, oi, ra);
> -    plugin_load_cb(env, addr, oi);
> +    if (cpu_plugin_mem_cbs_enabled(env_cpu(env))) {
> +        plugin_load_cb(env, addr, oi);
> +    }
>       return ret;
>   }
>   
> @@ -195,7 +205,9 @@ void cpu_stb_mmu(CPUArchState *env, abi_ptr addr, uint8_t val,
>                    MemOpIdx oi, uintptr_t retaddr)
>   {
>       helper_stb_mmu(env, addr, val, oi, retaddr);
> -    plugin_store_cb(env, addr, oi);
> +    if (cpu_plugin_mem_cbs_enabled(env_cpu(env))) {
> +        plugin_store_cb(env, addr, oi);
> +    }
>   }
>   
>   void cpu_stw_mmu(CPUArchState *env, abi_ptr addr, uint16_t val,
> @@ -203,7 +215,9 @@ void cpu_stw_mmu(CPUArchState *env, abi_ptr addr, uint16_t 
> val,
>   {
>       tcg_debug_assert((get_memop(oi) & MO_SIZE) == MO_16);
>       do_st2_mmu(env_cpu(env), addr, val, oi, retaddr);
> -    plugin_store_cb(env, addr, oi);
> +    if (cpu_plugin_mem_cbs_enabled(env_cpu(env))) {
> +        plugin_store_cb(env, addr, oi);
> +    }
>   }
>   
>   void cpu_stl_mmu(CPUArchState *env, abi_ptr addr, uint32_t val,
> @@ -211,7 +225,9 @@ void cpu_stl_mmu(CPUArchState *env, abi_ptr addr, uint32_t 
> val,
>   {
>       tcg_debug_assert((get_memop(oi) & MO_SIZE) == MO_32);
>       do_st4_mmu(env_cpu(env), addr, val, oi, retaddr);
> -    plugin_store_cb(env, addr, oi);
> +    if (cpu_plugin_mem_cbs_enabled(env_cpu(env))) {
> +        plugin_store_cb(env, addr, oi);
> +    }
>   }
>   
>   void cpu_stq_mmu(CPUArchState *env, abi_ptr addr, uint64_t val,
> @@ -219,7 +235,9 @@ void cpu_stq_mmu(CPUArchState *env, abi_ptr addr, uint64_t 
> val,
>   {
>       tcg_debug_assert((get_memop(oi) & MO_SIZE) == MO_64);
>       do_st8_mmu(env_cpu(env), addr, val, oi, retaddr);
> -    plugin_store_cb(env, addr, oi);
> +    if (cpu_plugin_mem_cbs_enabled(env_cpu(env))) {
> +        plugin_store_cb(env, addr, oi);
> +    }
>   }
>   
>   void cpu_st16_mmu(CPUArchState *env, abi_ptr addr, Int128 val,
> @@ -227,7 +245,9 @@ void cpu_st16_mmu(CPUArchState *env, abi_ptr addr, Int128 
> val,
>   {
>       tcg_debug_assert((get_memop(oi) & MO_SIZE) == MO_128);
>       do_st16_mmu(env_cpu(env), addr, val, oi, retaddr);
> -    plugin_store_cb(env, addr, oi);
> +    if (cpu_plugin_mem_cbs_enabled(env_cpu(env))) {
> +        plugin_store_cb(env, addr, oi);
> +    }
>   }
>   
>   /*