Re: [Qemu-devel] [PATCH v3 2/6] accel/tcg: Adding an optional tb execution counter

["Alex Bennée" <alex.bennee@linaro.org>]

vandersonmr <vandersonmr2@gmail.com> writes:

> We add the option to instrument each TB to
> count the number of times it is executed and
> store this in the its TBStatistics struct.
>
> Signed-off-by: Vanderson M. do Rosario <vandersonmr2@gmail.com>
> ---
>  accel/tcg/tcg-runtime.c   | 7 +++++++
>  accel/tcg/tcg-runtime.h   | 2 ++
>  accel/tcg/translator.c    | 1 +
>  include/exec/gen-icount.h | 9 +++++++++
>  4 files changed, 19 insertions(+)
>
> diff --git a/accel/tcg/tcg-runtime.c b/accel/tcg/tcg-runtime.c
> index 8a1e408e31..f332eae334 100644
> --- a/accel/tcg/tcg-runtime.c
> +++ b/accel/tcg/tcg-runtime.c
> @@ -167,3 +167,10 @@ void HELPER(exit_atomic)(CPUArchState *env)
>  {
>      cpu_loop_exit_atomic(env_cpu(env), GETPC());
>  }
> +
> +void HELPER(inc_exec_freq)(void *ptr)
> +{
> +    TBStatistics *stats = (TBStatistics *) ptr;
> +    g_assert(stats);
> +    atomic_inc(&stats->executions.total);
> +}
> diff --git a/accel/tcg/tcg-runtime.h b/accel/tcg/tcg-runtime.h
> index 4fa61b49b4..bf0b75dbe8 100644
> --- a/accel/tcg/tcg-runtime.h
> +++ b/accel/tcg/tcg-runtime.h
> @@ -28,6 +28,8 @@ DEF_HELPER_FLAGS_1(lookup_tb_ptr, TCG_CALL_NO_WG_SE, ptr, env)
>
>  DEF_HELPER_FLAGS_1(exit_atomic, TCG_CALL_NO_WG, noreturn, env)
>
> +DEF_HELPER_FLAGS_1(inc_exec_freq, TCG_CALL_NO_RWG, void, ptr)
> +
>  #ifdef CONFIG_SOFTMMU
>
>  DEF_HELPER_FLAGS_5(atomic_cmpxchgb, TCG_CALL_NO_WG,
> diff --git a/accel/tcg/translator.c b/accel/tcg/translator.c
> index 9226a348a3..cc06070e7e 100644
> --- a/accel/tcg/translator.c
> +++ b/accel/tcg/translator.c
> @@ -54,6 +54,7 @@ void translator_loop(const TranslatorOps *ops, DisasContextBase *db,
>      gen_tb_start(db->tb);
>      ops->tb_start(db, cpu);
>      tcg_debug_assert(db->is_jmp == DISAS_NEXT);  /* no early exit */
> +    gen_tb_exec_count(tb);
>
>      while (true) {
>          db->num_insns++;
> diff --git a/include/exec/gen-icount.h b/include/exec/gen-icount.h
> index f7669b6841..6701ab70c0 100644
> --- a/include/exec/gen-icount.h
> +++ b/include/exec/gen-icount.h
> @@ -7,6 +7,15 @@
>
>  static TCGOp *icount_start_insn;
>
> +static inline void gen_tb_exec_count(TranslationBlock *tb)
> +{
> +    if (qemu_loglevel_mask(CPU_LOG_HOT_TBS) && tb->tb_stats) {

so with the changes suggested in 1/6 it would become:

 if (tb->tb_stats && tb->tb_stats.stats_enabled & TB_EXEC_STATS) {

 }

which would eventually make the granularity controllable on a per-TB
basis. You could even hide the above check in a inline helper in the
headers (tb-stats.h?).

> +        TCGv_ptr ptr = tcg_const_ptr(tb->tb_stats);
> +        gen_helper_inc_exec_freq(ptr);
> +        tcg_temp_free_ptr(ptr);
> +    }
> +}
> +
>  static inline void gen_tb_start(TranslationBlock *tb)
>  {
>      TCGv_i32 count, imm;


--
Alex Bennée