Re: [Qemu-devel] [PATCH v5 02/10] accel: collecting TB execution count

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

vandersonmr <vandersonmr2@gmail.com> writes:

> If a TB has a TBS (TBStatistics) with the TB_EXEC_STATS
> enabled, then we instrument the start code of this TB
> to atomically count the number of times it is executed.
> We count both the number of "normal" executions and atomic
> executions of a TB.
>
> The execution count of the TB is stored in its respective
> TBS.
>
> All TBStatistics are created by default with the flags from
> default_tbstats_flag.
>
> Signed-off-by: Vanderson M. do Rosario <vandersonmr2@gmail.com>
> ---
>  accel/tcg/cpu-exec.c      |  4 ++++
>  accel/tcg/tb-stats.c      |  5 +++++
>  accel/tcg/tcg-runtime.c   |  7 +++++++
>  accel/tcg/tcg-runtime.h   |  2 ++
>  accel/tcg/translate-all.c |  7 +++++++
>  accel/tcg/translator.c    |  1 +
>  include/exec/gen-icount.h |  9 +++++++++
>  include/exec/tb-stats.h   | 19 +++++++++++++++++++
>  util/log.c                |  1 +
>  9 files changed, 55 insertions(+)
>
> diff --git a/accel/tcg/cpu-exec.c b/accel/tcg/cpu-exec.c
> index 6c85c3ee1e..e54be69499 100644
> --- a/accel/tcg/cpu-exec.c
> +++ b/accel/tcg/cpu-exec.c
> @@ -252,6 +252,10 @@ void cpu_exec_step_atomic(CPUState *cpu)
>
>          start_exclusive();
>
> +        if (tb_stats_enabled(tb, TB_EXEC_STATS)) {
> +            tb->tb_stats->executions.atomic++;
> +        }
> +
>          /* Since we got here, we know that parallel_cpus must be true.  */
>          parallel_cpus = false;
>          in_exclusive_region = true;
> diff --git a/accel/tcg/tb-stats.c b/accel/tcg/tb-stats.c
> index 02844717cb..3489133e9e 100644
> --- a/accel/tcg/tb-stats.c
> +++ b/accel/tcg/tb-stats.c
> @@ -37,3 +37,8 @@ bool tb_stats_collection_paused(void)
>  {
>      return tcg_collect_tb_stats == TB_STATS_PAUSED;
>  }
> +
> +uint32_t get_default_tbstats_flag(void)
> +{
> +    return default_tbstats_flag;
> +}
> diff --git a/accel/tcg/tcg-runtime.c b/accel/tcg/tcg-runtime.c
> index 8a1e408e31..6f4aafba11 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.normal);
> +}
> 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/translate-all.c b/accel/tcg/translate-all.c
> index b7bccacd3b..df08d183df 100644
> --- a/accel/tcg/translate-all.c
> +++ b/accel/tcg/translate-all.c
> @@ -1785,6 +1785,13 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
>       */
>      if (tb_stats_collection_enabled()) {
>          tb->tb_stats = tb_get_stats(phys_pc, pc, cs_base, flags, tb);
> +        uint32_t flag = get_default_tbstats_flag();
> +
> +        if (qemu_log_in_addr_range(tb->pc)) {

Minor nit: the compiler should spot it but you could move the flag
fetching inside this block.

> +            if (flag & TB_EXEC_STATS) {
> +                tb->tb_stats->stats_enabled |= TB_EXEC_STATS;
> +            }
> +        }
>      } else {
>          tb->tb_stats = NULL;
>      }
> diff --git a/accel/tcg/translator.c b/accel/tcg/translator.c
> index 9226a348a3..396a11e828 100644
> --- a/accel/tcg/translator.c
> +++ b/accel/tcg/translator.c
> @@ -46,6 +46,7 @@ void translator_loop(const TranslatorOps *ops, DisasContextBase *db,
>
>      ops->init_disas_context(db, cpu);
>      tcg_debug_assert(db->is_jmp == DISAS_NEXT);  /* no early exit */
> +    gen_tb_exec_count(tb);
>
>      /* Reset the temp count so that we can identify leaks */
>      tcg_clear_temp_count();
> diff --git a/include/exec/gen-icount.h b/include/exec/gen-icount.h
> index f7669b6841..b3efe41894 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 (tb_stats_enabled(tb, TB_EXEC_STATS)) {
> +        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;
> diff --git a/include/exec/tb-stats.h b/include/exec/tb-stats.h
> index cc8f8a6ce6..0265050b79 100644
> --- a/include/exec/tb-stats.h
> +++ b/include/exec/tb-stats.h
> @@ -6,6 +6,9 @@
>  #include "exec/tb-context.h"
>  #include "tcg.h"
>
> +#define tb_stats_enabled(tb, JIT_STATS) \
> +    (tb && tb->tb_stats && (tb->tb_stats->stats_enabled & JIT_STATS))
> +
>  typedef struct TBStatistics TBStatistics;
>
>  /*
> @@ -22,6 +25,15 @@ struct TBStatistics {
>      uint32_t     flags;
>      /* cs_base isn't included in the hash but we do check for matches */
>      target_ulong cs_base;
> +
> +    uint32_t stats_enabled;
> +
> +    /* Execution stats */
> +    struct {
> +        unsigned long normal;
> +        unsigned long atomic;
> +    } executions;
> +
>      /* current TB linked to this TBStatistics */
>      TranslationBlock *tb;
>  };
> @@ -32,7 +44,12 @@ void init_tb_stats_htable_if_not(void);
>
>  /* TBStatistic collection controls */
>  enum TBStatsStatus { TB_STATS_RUNNING, TB_STATS_PAUSED, TB_STATS_STOPPED };
> +
> +#define TB_NOTHING    0
> +#define TB_EXEC_STATS 1

As this is going to be a bit field you should use:

 #define TB_NOTHING (1 << 0)

etc...

> +
>  extern int tcg_collect_tb_stats;
> +extern uint32_t default_tbstats_flag;
>
>  void enable_collect_tb_stats(void);
>  void disable_collect_tb_stats(void);
> @@ -40,4 +57,6 @@ void pause_collect_tb_stats(void);
>  bool tb_stats_collection_enabled(void);
>  bool tb_stats_collection_paused(void);
>
> +uint32_t get_default_tbstats_flag(void);
> +
>  #endif
> diff --git a/util/log.c b/util/log.c
> index 393a17115b..29021a4584 100644
> --- a/util/log.c
> +++ b/util/log.c
> @@ -32,6 +32,7 @@ static int log_append = 0;
>  static GArray *debug_regions;
>
>  int tcg_collect_tb_stats;
> +uint32_t default_tbstats_flag;

This should static and in tb_stats.c (like the helper is)

>
>  /* Return the number of characters emitted.  */
>  int qemu_log(const char *fmt, ...)


--
Alex Bennée