RISCV_CPU(cs) uses a checked cast.  When QOM cast debugging is enabled
this adds about 5% total overhead when emulating RV64 on x86-64 host.

Using a RISC-V guest with 16 vCPUs, 16 GB of guest RAM, virtio-blk
disk.  The guest has a copy of the qemu source tree.  The test
involves compiling the qemu source tree with 'make clean; time make -j16'.

Before making this change the compile step took 449 & 447 seconds over
two consecutive runs.

After making this change: 428 & 421 seconds.

The saving is over 5%.

Thanks: Paolo Bonzini
Thanks: Philippe Mathieu-Daudé
Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
---
 target/riscv/cpu_helper.c | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
index 3a02079290..8c28241c18 100644
--- a/target/riscv/cpu_helper.c
+++ b/target/riscv/cpu_helper.c
@@ -65,8 +65,7 @@ int riscv_cpu_mmu_index(CPURISCVState *env, bool ifetch)
 void cpu_get_tb_cpu_state(CPURISCVState *env, vaddr *pc,
                           uint64_t *cs_base, uint32_t *pflags)
 {
-    CPUState *cs = env_cpu(env);
-    RISCVCPU *cpu = RISCV_CPU(cs);
+    RISCVCPU *cpu = env_archcpu(env);
     RISCVExtStatus fs, vs;
     uint32_t flags = 0;
 
-- 
2.41.0

On Mon, Oct 9, 2023 at 10:50 PM Richard W.M. Jones <rjones@redhat.com> wrote:
>
> RISCV_CPU(cs) uses a checked cast.  When QOM cast debugging is enabled
> this adds about 5% total overhead when emulating RV64 on x86-64 host.
>
> Using a RISC-V guest with 16 vCPUs, 16 GB of guest RAM, virtio-blk
> disk.  The guest has a copy of the qemu source tree.  The test
> involves compiling the qemu source tree with 'make clean; time make -j16'.
>
> Before making this change the compile step took 449 & 447 seconds over
> two consecutive runs.
>
> After making this change: 428 & 421 seconds.
>
> The saving is over 5%.
>
> Thanks: Paolo Bonzini
> Thanks: Philippe Mathieu-Daudé
> Signed-off-by: Richard W.M. Jones <rjones@redhat.com>

Thanks!

Applied to riscv-to-apply.next

Alistair

> ---
>  target/riscv/cpu_helper.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
> index 3a02079290..8c28241c18 100644
> --- a/target/riscv/cpu_helper.c
> +++ b/target/riscv/cpu_helper.c
> @@ -65,8 +65,7 @@ int riscv_cpu_mmu_index(CPURISCVState *env, bool ifetch)
>  void cpu_get_tb_cpu_state(CPURISCVState *env, vaddr *pc,
>                            uint64_t *cs_base, uint32_t *pflags)
>  {
> -    CPUState *cs = env_cpu(env);
> -    RISCVCPU *cpu = RISCV_CPU(cs);
> +    RISCVCPU *cpu = env_archcpu(env);
>      RISCVExtStatus fs, vs;
>      uint32_t flags = 0;
>
> --
> 2.41.0
>
>

On Mon, Oct 9, 2023 at 10:50 PM Richard W.M. Jones <rjones@redhat.com> wrote:
>
> RISCV_CPU(cs) uses a checked cast.  When QOM cast debugging is enabled
> this adds about 5% total overhead when emulating RV64 on x86-64 host.
>
> Using a RISC-V guest with 16 vCPUs, 16 GB of guest RAM, virtio-blk
> disk.  The guest has a copy of the qemu source tree.  The test
> involves compiling the qemu source tree with 'make clean; time make -j16'.
>
> Before making this change the compile step took 449 & 447 seconds over
> two consecutive runs.
>
> After making this change: 428 & 421 seconds.
>
> The saving is over 5%.
>
> Thanks: Paolo Bonzini
> Thanks: Philippe Mathieu-Daudé
> Signed-off-by: Richard W.M. Jones <rjones@redhat.com>

Reviewed-by: Alistair Francis <alistair.francis@wdc.com>

Alistair

> ---
>  target/riscv/cpu_helper.c | 3 +--
>  1 file changed, 1 insertion(+), 2 deletions(-)
>
> diff --git a/target/riscv/cpu_helper.c b/target/riscv/cpu_helper.c
> index 3a02079290..8c28241c18 100644
> --- a/target/riscv/cpu_helper.c
> +++ b/target/riscv/cpu_helper.c
> @@ -65,8 +65,7 @@ int riscv_cpu_mmu_index(CPURISCVState *env, bool ifetch)
>  void cpu_get_tb_cpu_state(CPURISCVState *env, vaddr *pc,
>                            uint64_t *cs_base, uint32_t *pflags)
>  {
> -    CPUState *cs = env_cpu(env);
> -    RISCVCPU *cpu = RISCV_CPU(cs);
> +    RISCVCPU *cpu = env_archcpu(env);
>      RISCVExtStatus fs, vs;
>      uint32_t flags = 0;
>
> --
> 2.41.0
>
>

On 10/9/23 05:48, Richard W.M. Jones wrote:
> RISCV_CPU(cs) uses a checked cast.  When QOM cast debugging is enabled
> this adds about 5% total overhead when emulating RV64 on x86-64 host.
> 
> Using a RISC-V guest with 16 vCPUs, 16 GB of guest RAM, virtio-blk
> disk.  The guest has a copy of the qemu source tree.  The test
> involves compiling the qemu source tree with 'make clean; time make -j16'.
> 
> Before making this change the compile step took 449 & 447 seconds over
> two consecutive runs.
> 
> After making this change: 428 & 421 seconds.
> 
> The saving is over 5%.
> 
> Thanks: Paolo Bonzini
> Thanks: Philippe Mathieu-Daudé
> Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
> ---
>   target/riscv/cpu_helper.c | 3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)

Reviewed-by: Richard Henderson <richard.henderson@linaro.org>


r~

On 9/10/23 14:48, Richard W.M. Jones wrote:
> RISCV_CPU(cs) uses a checked cast.  When QOM cast debugging is enabled
> this adds about 5% total overhead when emulating RV64 on x86-64 host.
> 
> Using a RISC-V guest with 16 vCPUs, 16 GB of guest RAM, virtio-blk
> disk.  The guest has a copy of the qemu source tree.  The test
> involves compiling the qemu source tree with 'make clean; time make -j16'.
> 
> Before making this change the compile step took 449 & 447 seconds over
> two consecutive runs.
> 
> After making this change: 428 & 421 seconds.
> 
> The saving is over 5%.
> 
> Thanks: Paolo Bonzini
> Thanks: Philippe Mathieu-Daudé
> Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
> ---
>   target/riscv/cpu_helper.c | 3 +--
>   1 file changed, 1 insertion(+), 2 deletions(-)

Reviewed-by: Philippe Mathieu-Daudé <philmd@linaro.org>