[Qemu-devel] [PATCH v4 1/7] accel: introducing TBStatistics structure

[vandersonmr]

To store statistics for each TB we created a TBStatistics structure
which is linked with the TBs. The TBStatistics can stay alive after
tb_flush and be relinked to a regenerated TB. So the statistics can
be accumulated even through flushes.

TBStatistics will be also referred to as TBS or tbstats.

Signed-off-by: Vanderson M. do Rosario <address@hidden>
---
 accel/tcg/translate-all.c | 57 +++++++++++++++++++++++++++++++++++++++
 include/exec/exec-all.h   | 15 +++--------
 include/exec/tb-context.h | 12 +++++++++
 include/exec/tb-hash.h    |  7 +++++
 include/exec/tb-stats.h   | 29 ++++++++++++++++++++
 include/qemu/log.h        |  6 +++++
 util/log.c                | 28 +++++++++++++++++++
 7 files changed, 143 insertions(+), 11 deletions(-)
 create mode 100644 include/exec/tb-stats.h

diff --git a/accel/tcg/translate-all.c b/accel/tcg/translate-all.c
index 5d1e08b169..a574890a80 100644
--- a/accel/tcg/translate-all.c
+++ b/accel/tcg/translate-all.c
@@ -1118,6 +1118,23 @@ static inline void code_gen_alloc(size_t tb_size)
     }
 }
 
+/*
+ * This is the more or less the same compare, but the data persists
+ * over tb_flush. We also aggregate the various variations of cflags
+ * under one record and ignore the details of page overlap (although
+ * we can count it).
+ */
+bool tb_stats_cmp(const void *ap, const void *bp)
+{
+    const TBStatistics *a = ap;
+    const TBStatistics *b = bp;
+
+    return a->phys_pc == b->phys_pc &&
+        a->pc == b->pc &&
+        a->cs_base == b->cs_base &&
+        a->flags == b->flags;
+}
+
 static bool tb_cmp(const void *ap, const void *bp)
 {
     const TranslationBlock *a = ap;
@@ -1137,6 +1154,9 @@ static void tb_htable_init(void)
     unsigned int mode = QHT_MODE_AUTO_RESIZE;
 
     qht_init(&tb_ctx.htable, tb_cmp, CODE_GEN_HTABLE_SIZE, mode);
+    if (tb_stats_collection_enabled()) {
+        qht_init(&tb_ctx.tb_stats, tb_stats_cmp, CODE_GEN_HTABLE_SIZE, mode);
+    }
 }
 
 /* Must be called before using the QEMU cpus. 'tb_size' is the size
@@ -1666,6 +1686,32 @@ tb_link_page(TranslationBlock *tb, tb_page_addr_t 
phys_pc,
     return tb;
 }
 
+static TBStatistics *tb_get_stats(tb_page_addr_t phys_pc, target_ulong pc,
+                                  target_ulong cs_base, uint32_t flags)
+{
+    TBStatistics *new_stats = g_new0(TBStatistics, 1);
+    uint32_t hash = tb_stats_hash_func(phys_pc, pc, flags);
+    void *existing_stats = NULL;
+    new_stats->phys_pc = phys_pc;
+    new_stats->pc = pc;
+    new_stats->cs_base = cs_base;
+    new_stats->flags = flags;
+
+    qht_insert(&tb_ctx.tb_stats, new_stats, hash, &existing_stats);
+
+    if (unlikely(existing_stats)) {
+        /*
+         * If there is already a TBStatistic for this TB from a previous flush
+         * then just make the new TB point to the older TBStatistic
+         */
+        g_free(new_stats);
+        return existing_stats;
+    } else {
+        return new_stats;
+    }
+}
+
+
 /* Called with mmap_lock held for user mode emulation.  */
 TranslationBlock *tb_gen_code(CPUState *cpu,
                               target_ulong pc, target_ulong cs_base,
@@ -1732,6 +1778,17 @@ TranslationBlock *tb_gen_code(CPUState *cpu,
     ti = profile_getclock();
 #endif
 
+    /*
+     * We want to fetch the stats structure before we start code
+     * generation so we can count interesting things about this
+     * generation.
+     */
+    if (tb_stats_collection_enabled()) {
+        tb->tb_stats = tb_get_stats(phys_pc, pc, cs_base, flags);
+    } else {
+        tb->tb_stats = NULL;
+    }
+
     tcg_func_start(tcg_ctx);
 
     tcg_ctx->cpu = env_cpu(env);
diff --git a/include/exec/exec-all.h b/include/exec/exec-all.h
index 16034ee651..24bd6a0a0c 100644
--- a/include/exec/exec-all.h
+++ b/include/exec/exec-all.h
@@ -22,21 +22,11 @@
 
 #include "exec/tb-context.h"
 #include "sysemu/cpus.h"
+#include "exec/tb-stats.h"
 
 /* allow to see translation results - the slowdown should be negligible, so we 
leave it */
 #define DEBUG_DISAS
 
-/* Page tracking code uses ram addresses in system mode, and virtual
-   addresses in userspace mode.  Define tb_page_addr_t to be an appropriate
-   type.  */
-#if defined(CONFIG_USER_ONLY)
-typedef abi_ulong tb_page_addr_t;
-#define TB_PAGE_ADDR_FMT TARGET_ABI_FMT_lx
-#else
-typedef ram_addr_t tb_page_addr_t;
-#define TB_PAGE_ADDR_FMT RAM_ADDR_FMT
-#endif
-
 #include "qemu/log.h"
 
 void gen_intermediate_code(CPUState *cpu, TranslationBlock *tb, int max_insns);
@@ -403,6 +393,9 @@ struct TranslationBlock {
     uintptr_t jmp_list_head;
     uintptr_t jmp_list_next[2];
     uintptr_t jmp_dest[2];
+
+    /* Pointer to a struct where statistics from the TB is stored */
+    TBStatistics *tb_stats;
 };
 
 extern bool parallel_cpus;
diff --git a/include/exec/tb-context.h b/include/exec/tb-context.h
index feb585e0a7..3cfb62a338 100644
--- a/include/exec/tb-context.h
+++ b/include/exec/tb-context.h
@@ -23,6 +23,17 @@
 #include "qemu/thread.h"
 #include "qemu/qht.h"
 
+/* Page tracking code uses ram addresses in system mode, and virtual
+   addresses in userspace mode.  Define tb_page_addr_t to be an appropriate
+   type.  */
+#if defined(CONFIG_USER_ONLY)
+typedef abi_ulong tb_page_addr_t;
+#define TB_PAGE_ADDR_FMT TARGET_ABI_FMT_lx
+#else
+typedef ram_addr_t tb_page_addr_t;
+#define TB_PAGE_ADDR_FMT RAM_ADDR_FMT
+#endif
+
 #define CODE_GEN_HTABLE_BITS     15
 #define CODE_GEN_HTABLE_SIZE     (1 << CODE_GEN_HTABLE_BITS)
 
@@ -35,6 +46,7 @@ struct TBContext {
 
     /* statistics */
     unsigned tb_flush_count;
+    struct qht tb_stats;
 };
 
 extern TBContext tb_ctx;
diff --git a/include/exec/tb-hash.h b/include/exec/tb-hash.h
index 4f3a37d927..54c477fe79 100644
--- a/include/exec/tb-hash.h
+++ b/include/exec/tb-hash.h
@@ -64,4 +64,11 @@ uint32_t tb_hash_func(tb_page_addr_t phys_pc, target_ulong 
pc, uint32_t flags,
     return qemu_xxhash7(phys_pc, pc, flags, cf_mask, trace_vcpu_dstate);
 }
 
+static inline
+uint32_t tb_stats_hash_func(tb_page_addr_t phys_pc, target_ulong pc,
+                            uint32_t flags)
+{
+    return qemu_xxhash5(phys_pc, pc, flags);
+}
+
 #endif
diff --git a/include/exec/tb-stats.h b/include/exec/tb-stats.h
new file mode 100644
index 0000000000..0913155ec3
--- /dev/null
+++ b/include/exec/tb-stats.h
@@ -0,0 +1,29 @@
+#ifndef TB_STATS_H
+
+#define TB_STATS_H
+
+#include "exec/cpu-common.h"
+#include "exec/tb-context.h"
+#include "tcg.h"
+
+typedef struct TBStatistics TBStatistics;
+
+/*
+ * This struct stores statistics such as execution count of the
+ * TranslationBlocks. Each sets of TBs for a given phys_pc/pc/flags
+ * has its own TBStatistics which will persist over tb_flush.
+ *
+ * We include additional counters to track number of translations as
+ * well as variants for compile flags.
+ */
+struct TBStatistics {
+    tb_page_addr_t phys_pc;
+    target_ulong pc;
+    uint32_t     flags;
+    /* cs_base isn't included in the hash but we do check for matches */
+    target_ulong cs_base;
+};
+
+bool tb_stats_cmp(const void *ap, const void *bp);
+
+#endif
diff --git a/include/qemu/log.h b/include/qemu/log.h
index b097a6cae1..e175d4d5d0 100644
--- a/include/qemu/log.h
+++ b/include/qemu/log.h
@@ -129,4 +129,10 @@ void qemu_log_flush(void);
 /* Close the log file */
 void qemu_log_close(void);
 
+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);
+
 #endif
diff --git a/util/log.c b/util/log.c
index 1d1b33f7d9..ab73fdc100 100644
--- a/util/log.c
+++ b/util/log.c
@@ -326,3 +326,31 @@ void qemu_print_log_usage(FILE *f)
     fprintf(f, "\nUse \"-d trace:help\" to get a list of trace events.\n\n");
 #endif
 }
+
+int tcg_collect_tb_stats;
+
+void enable_collect_tb_stats(void)
+{
+    tcg_collect_tb_stats = 1;
+}
+
+void disable_collect_tb_stats(void)
+{
+    tcg_collect_tb_stats = 0;
+}
+
+void pause_collect_tb_stats(void)
+{
+    tcg_collect_tb_stats = 2;
+}
+
+bool tb_stats_collection_enabled(void)
+{
+    return tcg_collect_tb_stats;
+}
+
+bool tb_stats_collection_paused(void)
+{
+    return tcg_collect_tb_stats == 2;
+}
+
-- 
2.22.0