[Qemu-devel] [PULL 15/15] translate-all: add tb hash bucket info to 'info jit' dump

[Richard Henderson]

From: "Emilio G. Cota" <address@hidden>

Examples:

- Good hashing, i.e. tb_hash_func5(phys_pc, pc, flags):
TB count            715135/2684354
[...]
TB hash buckets     388775/524288 (74.15% head buckets used)
TB hash occupancy   33.04% avg chain occ. Histogram: [0,10)%|▆ █  
▅▁▃▁▁|[90,100]%
TB hash avg chain   1.017 buckets. Histogram: 1|█▁▁|3

- Not-so-good hashing, i.e. tb_hash_func5(phys_pc, pc, 0):
TB count            712636/2684354
[...]
TB hash buckets     344924/524288 (65.79% head buckets used)
TB hash occupancy   31.64% avg chain occ. Histogram: [0,10)%|█ ▆  
▅▁▃▁▂|[90,100]%
TB hash avg chain   1.047 buckets. Histogram: 1|█▁▁▁|4

- Bad hashing, i.e. tb_hash_func5(phys_pc, 0, 0):
TB count            702818/2684354
[...]
TB hash buckets     112741/524288 (21.50% head buckets used)
TB hash occupancy   10.15% avg chain occ. Histogram: [0,10)%|█ ▁  
▁▁▁▁▁|[90,100]%
TB hash avg chain   2.107 buckets. Histogram: [1.0,10.2)|█▁▁▁▁▁▁▁▁▁|[83.8,93.0]

- Good hashing, but no auto-resize:
TB count            715634/2684354
TB hash buckets     8192/8192 (100.00% head buckets used)
TB hash occupancy   98.30% avg chain occ. Histogram: 
[95.3,95.8)%|▁▁▃▄▃▄▁▇▁█|[99.5,100.0]%
TB hash avg chain   22.070 buckets. Histogram: 
[15.0,16.7)|▁▂▅▄█▅▁▁▁▁|[30.3,32.0]

Acked-by: Sergey Fedorov <address@hidden>
Suggested-by: Richard Henderson <address@hidden>
Reviewed-by: Richard Henderson <address@hidden>
Signed-off-by: Emilio G. Cota <address@hidden>
Message-Id: <address@hidden>
Signed-off-by: Richard Henderson <address@hidden>
---
 translate-all.c | 36 ++++++++++++++++++++++++++++++++++++
 1 file changed, 36 insertions(+)

diff --git a/translate-all.c b/translate-all.c
index b620fcc..e8b88b4 100644
--- a/translate-all.c
+++ b/translate-all.c
@@ -1668,6 +1668,10 @@ void dump_exec_info(FILE *f, fprintf_function 
cpu_fprintf)
     int i, target_code_size, max_target_code_size;
     int direct_jmp_count, direct_jmp2_count, cross_page;
     TranslationBlock *tb;
+    struct qht_stats hst;
+    uint32_t hgram_opts;
+    size_t hgram_bins;
+    char *hgram;
 
     target_code_size = 0;
     max_target_code_size = 0;
@@ -1718,6 +1722,38 @@ void dump_exec_info(FILE *f, fprintf_function 
cpu_fprintf)
                 direct_jmp2_count,
                 tcg_ctx.tb_ctx.nb_tbs ? (direct_jmp2_count * 100) /
                         tcg_ctx.tb_ctx.nb_tbs : 0);
+
+    qht_statistics_init(&tcg_ctx.tb_ctx.htable, &hst);
+
+    cpu_fprintf(f, "TB hash buckets     %zu/%zu (%0.2f%% head buckets used)\n",
+                hst.used_head_buckets, hst.head_buckets,
+                (double)hst.used_head_buckets / hst.head_buckets * 100);
+
+    hgram_opts =  QDIST_PR_BORDER | QDIST_PR_LABELS;
+    hgram_opts |= QDIST_PR_100X   | QDIST_PR_PERCENT;
+    if (qdist_xmax(&hst.occupancy) - qdist_xmin(&hst.occupancy) == 1) {
+        hgram_opts |= QDIST_PR_NODECIMAL;
+    }
+    hgram = qdist_pr(&hst.occupancy, 10, hgram_opts);
+    cpu_fprintf(f, "TB hash occupancy   %0.2f%% avg chain occ. Histogram: 
%s\n",
+                qdist_avg(&hst.occupancy) * 100, hgram);
+    g_free(hgram);
+
+    hgram_opts = QDIST_PR_BORDER | QDIST_PR_LABELS;
+    hgram_bins = qdist_xmax(&hst.chain) - qdist_xmin(&hst.chain);
+    if (hgram_bins > 10) {
+        hgram_bins = 10;
+    } else {
+        hgram_bins = 0;
+        hgram_opts |= QDIST_PR_NODECIMAL | QDIST_PR_NOBINRANGE;
+    }
+    hgram = qdist_pr(&hst.chain, hgram_bins, hgram_opts);
+    cpu_fprintf(f, "TB hash avg chain   %0.3f buckets. Histogram: %s\n",
+                qdist_avg(&hst.chain), hgram);
+    g_free(hgram);
+
+    qht_statistics_destroy(&hst);
+
     cpu_fprintf(f, "\nStatistics:\n");
     cpu_fprintf(f, "TB flush count      %d\n", tcg_ctx.tb_ctx.tb_flush_count);
     cpu_fprintf(f, "TB invalidate count %d\n",
-- 
2.5.5