Re: [Qemu-devel] [PATCH v4 2/7] 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 the TB
> to atomically count the number of times it is executed.
> The execution count of the TB is stored in its respective
> TBS.
>
> Signed-off-by: Vanderson M. do Rosario <vandersonmr2@gmail.com>
> ---
>  accel/tcg/tcg-runtime.c   |  7 +++++++
>  accel/tcg/tcg-runtime.h   |  2 ++
>  accel/tcg/translate-all.c |  8 ++++++++
>  accel/tcg/translator.c    |  1 +
>  include/exec/gen-icount.h |  9 +++++++++
>  include/exec/tb-stats.h   | 11 +++++++++++
>  include/qemu/log.h        |  6 ++++++
>  util/log.c                | 11 +++++++++++
>  8 files changed, 55 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/translate-all.c b/accel/tcg/translate-all.c
> index a574890a80..7497dae508 100644
> --- a/accel/tcg/translate-all.c
> +++ b/accel/tcg/translate-all.c
> @@ -1785,6 +1785,14 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
>       */
>      if (tb_stats_collection_enabled()) {
>          tb->tb_stats = tb_get_stats(phys_pc, pc, cs_base, flags);
> +        uint32_t flag = get_default_tbstats_flag();
> +
> +        if (qemu_log_in_addr_range(tb->pc)) {
> +            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 0913155ec3..ee1e8de0d3 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 +25,14 @@ 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 total;
> +        unsigned long atomic;

We are not incrementing atomic in this patch. Also it's not total so
maybe "normal" makes more sense. Something like:

fixup! accel: collecting TB execution count

4 files changed, 11 insertions(+), 6 deletions(-)
accel/tcg/cpu-exec.c    | 4 ++++
accel/tcg/tb-stats.c    | 9 +++++----
accel/tcg/tcg-runtime.c | 2 +-
include/exec/tb-stats.h | 2 +-

modified   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;
modified   accel/tcg/tb-stats.c
@@ -233,11 +233,12 @@ static void dump_tb_header(TBStatistics *tbs)
     float guest_host_prop = g ? ((float) h / g) : 0;

     qemu_log("TB%d: phys:0x"TB_PAGE_ADDR_FMT" virt:0x"TARGET_FMT_lx
-             " flags:%#08x (trans:%lu uncached:%lu exec:%lu ints: g:%u op:%u op_opt:%u h:%u h/g:%.2f spills:%d)\n",
+             " flags:%#08x (trans:%lu uncached:%lu exec:%lu/%lu ints: g:%u op:%u op_opt:%u h:%u h/g:%.2f spills:%d)\n",
              tbs->display_id,
              tbs->phys_pc, tbs->pc, tbs->flags,
              tbs->translations.total, tbs->translations.uncached,
-             tbs->executions.total, g, ops, ops_opt, h, guest_host_prop,
+             tbs->executions.normal, tbs->executions.atomic,
+             g, ops, ops_opt, h, guest_host_prop,
              spills);
 }

@@ -254,8 +255,8 @@ inverse_sort_tbs(gconstpointer p1, gconstpointer p2, gpointer psort_by)
         c1 = tbs1->code.spills;
         c2 = tbs2->code.spills;
     } else if (likely(sort_by == SORT_BY_HOTNESS)) {
-        c1 = tbs1->executions.total;
-        c2 = tbs2->executions.total;
+        c1 = tbs1->executions.normal;
+        c2 = tbs2->executions.normal;
     } else if (likely(sort_by == SORT_BY_HG)) {
         if (tbs1->code.num_guest_inst == 0) {
             return -1;
modified   accel/tcg/tcg-runtime.c
@@ -172,5 +172,5 @@ void HELPER(inc_exec_freq)(void *ptr)
 {
     TBStatistics *stats = (TBStatistics *) ptr;
     g_assert(stats);
-    atomic_inc(&stats->executions.total);
+    atomic_inc(&stats->executions.normal);
 }
modified   include/exec/tb-stats.h
@@ -33,7 +33,7 @@ struct TBStatistics {

     /* Execution stats */
     struct {
-        unsigned long total;
+        unsigned long normal;
         unsigned long atomic;
     } executions;

> diff --git a/include/qemu/log.h b/include/qemu/log.h
> index e175d4d5d0..b213411836 100644
> --- a/include/qemu/log.h
> +++ b/include/qemu/log.h
> @@ -129,10 +129,16 @@ void qemu_log_flush(void);
>  /* Close the log file */
>  void qemu_log_close(void);
>
> +#define TB_NOTHING    0
> +#define TB_EXEC_STATS (1 << 1)
> +
>  void enable_collect_tb_stats(void);
>  void disable_collect_tb_stats(void);
>  void pause_collect_tb_stats(void);
>  bool tb_stats_collection_enabled(void);
>  bool tb_stats_collection_paused(void);
>
> +void set_default_tbstats_flag(uint32_t flag);
> +uint32_t get_default_tbstats_flag(void);
> +
>  #endif
> diff --git a/util/log.c b/util/log.c
> index ab73fdc100..f81653d712 100644
> --- a/util/log.c
> +++ b/util/log.c
> @@ -354,3 +354,14 @@ bool tb_stats_collection_paused(void)
>      return tcg_collect_tb_stats == 2;
>  }
>
> +uint32_t default_tbstats_flag;
> +
> +void set_default_tbstats_flag(uint32_t flag)
> +{
> +    default_tbstats_flag = flag;
> +}
> +
> +uint32_t get_default_tbstats_flag(void)
> +{
> +    return default_tbstats_flag;
> +}

Some comment about not overloading log.c as before.

--
Alex Bennée