[Qemu-devel] [PATCH v2 2/4] Adding an optional tb execution counter.

[vandersonmr <vandersonmr2@gmail.com>]

We collect the number of times each TB is executed
and store it in the its TBStatistics.
We also count the number of times the execution counter overflows.

Signed-off-by: Vanderson M. do Rosario <vandersonmr2@gmail.com>
---
 accel/tcg/tcg-runtime.c   | 10 ++++++++++
 accel/tcg/tcg-runtime.h   |  2 ++
 accel/tcg/translator.c    |  1 +
 include/exec/gen-icount.h |  9 +++++++++
 4 files changed, 22 insertions(+)

diff --git a/accel/tcg/tcg-runtime.c b/accel/tcg/tcg-runtime.c
index 8a1e408e31..9888a7fce8 100644
--- a/accel/tcg/tcg-runtime.c
+++ b/accel/tcg/tcg-runtime.c
@@ -167,3 +167,13 @@ void HELPER(exit_atomic)(CPUArchState *env)
 {
     cpu_loop_exit_atomic(env_cpu(env), GETPC());
 }
+
+void HELPER(inc_exec_freq)(void *ptr)
+{
+    TranslationBlock *tb = (TranslationBlock*) ptr;
+    // if overflows, then reset the execution counter and increment the overflow counter
+    if (atomic_cmpxchg(&tb->tb_stats->exec_count, 0xFFFFFFFF, 0) == 0xFFFFFFFF) {
+        atomic_inc(&tb->tb_stats->exec_count_overflows);
+    }
+    atomic_inc(&tb->tb_stats->exec_count);
+}
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..6d38b6e1fb 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)) {
+    TCGv_ptr tb_ptr = tcg_const_ptr(tb);
+    gen_helper_inc_exec_freq(tb_ptr);
+    tcg_temp_free_ptr(tb_ptr);
+  }
+}
+
 static inline void gen_tb_start(TranslationBlock *tb)
 {
     TCGv_i32 count, imm;
-- 
2.22.0