target/linux/generic/patches-3.18/080-02-fib_trie-Update-usage-stats-to-be-percpu-instead-of-.patch

   1 From: Alexander Duyck <alexander.h.duyck@redhat.com>
   2 Date: Wed, 31 Dec 2014 10:55:29 -0800
   3 Subject: [PATCH] fib_trie: Update usage stats to be percpu instead of
   4  global variables
   5
   6 The trie usage stats were currently being shared by all threads that were
   7 calling fib_table_lookup.  As a result when multiple threads were
   8 performing lookups simultaneously the trie would begin to cache bounce
   9 between those threads.
  10
  11 In order to prevent this I have updated the usage stats to use a set of
  12 percpu variables.  By doing this we should be able to avoid the cache
  13 bouncing and still make use of these stats.
  14
  15 Signed-off-by: Alexander Duyck <alexander.h.duyck@redhat.com>
  16 Signed-off-by: David S. Miller <davem@davemloft.net>
  17 ---
  18
  19 --- a/net/ipv4/fib_frontend.c
  20 +++ b/net/ipv4/fib_frontend.c
  21 @@ -67,7 +67,7 @@ static int __net_init fib4_rules_init(st
  22         return 0;
  23
  24  fail:
  25 -       kfree(local_table);
  26 +       fib_free_table(local_table);
  27         return -ENOMEM;
  28  }
  29  #else
  30 --- a/net/ipv4/fib_trie.c
  31 +++ b/net/ipv4/fib_trie.c
  32 @@ -153,7 +153,7 @@ struct trie_stat {
  33  struct trie {
  34         struct rt_trie_node __rcu *trie;
  35  #ifdef CONFIG_IP_FIB_TRIE_STATS
  36 -       struct trie_use_stats stats;
  37 +       struct trie_use_stats __percpu *stats;
  38  #endif
  39  };
  40
  41 @@ -631,7 +631,7 @@ static struct rt_trie_node *resize(struc
  42                 if (IS_ERR(tn)) {
  43                         tn = old_tn;
  44  #ifdef CONFIG_IP_FIB_TRIE_STATS
  45 -                       t->stats.resize_node_skipped++;
  46 +                       this_cpu_inc(t->stats->resize_node_skipped);
  47  #endif
  48                         break;
  49                 }
  50 @@ -658,7 +658,7 @@ static struct rt_trie_node *resize(struc
  51                 if (IS_ERR(tn)) {
  52                         tn = old_tn;
  53  #ifdef CONFIG_IP_FIB_TRIE_STATS
  54 -                       t->stats.resize_node_skipped++;
  55 +                       this_cpu_inc(t->stats->resize_node_skipped);
  56  #endif
  57                         break;
  58                 }
  59 @@ -1357,7 +1357,7 @@ static int check_leaf(struct fib_table *
  60                         err = fib_props[fa->fa_type].error;
  61                         if (err) {
  62  #ifdef CONFIG_IP_FIB_TRIE_STATS
  63 -                               t->stats.semantic_match_passed++;
  64 +                               this_cpu_inc(t->stats->semantic_match_passed);
  65  #endif
  66                                 return err;
  67                         }
  68 @@ -1372,7 +1372,7 @@ static int check_leaf(struct fib_table *
  69                                         continue;
  70
  71  #ifdef CONFIG_IP_FIB_TRIE_STATS
  72 -                               t->stats.semantic_match_passed++;
  73 +                               this_cpu_inc(t->stats->semantic_match_passed);
  74  #endif
  75                                 res->prefixlen = li->plen;
  76                                 res->nh_sel = nhsel;
  77 @@ -1388,7 +1388,7 @@ static int check_leaf(struct fib_table *
  78                 }
  79
  80  #ifdef CONFIG_IP_FIB_TRIE_STATS
  81 -               t->stats.semantic_match_miss++;
  82 +               this_cpu_inc(t->stats->semantic_match_miss);
  83  #endif
  84         }
  85
  86 @@ -1399,6 +1399,9 @@ int fib_table_lookup(struct fib_table *t
  87                      struct fib_result *res, int fib_flags)
  88  {
  89         struct trie *t = (struct trie *) tb->tb_data;
  90 +#ifdef CONFIG_IP_FIB_TRIE_STATS
  91 +       struct trie_use_stats __percpu *stats = t->stats;
  92 +#endif
  93         int ret;
  94         struct rt_trie_node *n;
  95         struct tnode *pn;
  96 @@ -1417,7 +1420,7 @@ int fib_table_lookup(struct fib_table *t
  97                 goto failed;
  98
  99  #ifdef CONFIG_IP_FIB_TRIE_STATS
 100 -       t->stats.gets++;
 101 +       this_cpu_inc(stats->gets);
 102  #endif
 103
 104         /* Just a leaf? */
 105 @@ -1441,7 +1444,7 @@ int fib_table_lookup(struct fib_table *t
 106
 107                 if (n == NULL) {
 108  #ifdef CONFIG_IP_FIB_TRIE_STATS
 109 -                       t->stats.null_node_hit++;
 110 +                       this_cpu_inc(stats->null_node_hit);
 111  #endif
 112                         goto backtrace;
 113                 }
 114 @@ -1576,7 +1579,7 @@ backtrace:
 115                         chopped_off = 0;
 116
 117  #ifdef CONFIG_IP_FIB_TRIE_STATS
 118 -                       t->stats.backtrack++;
 119 +                       this_cpu_inc(stats->backtrack);
 120  #endif
 121                         goto backtrace;
 122                 }
 123 @@ -1830,6 +1833,11 @@ int fib_table_flush(struct fib_table *tb
 124
 125  void fib_free_table(struct fib_table *tb)
 126  {
 127 +#ifdef CONFIG_IP_FIB_TRIE_STATS
 128 +       struct trie *t = (struct trie *)tb->tb_data;
 129 +
 130 +       free_percpu(t->stats);
 131 +#endif /* CONFIG_IP_FIB_TRIE_STATS */
 132         kfree(tb);
 133  }
 134
 135 @@ -1973,7 +1981,14 @@ struct fib_table *fib_trie_table(u32 id)
 136         tb->tb_num_default = 0;
 137
 138         t = (struct trie *) tb->tb_data;
 139 -       memset(t, 0, sizeof(*t));
 140 +       RCU_INIT_POINTER(t->trie, NULL);
 141 +#ifdef CONFIG_IP_FIB_TRIE_STATS
 142 +       t->stats = alloc_percpu(struct trie_use_stats);
 143 +       if (!t->stats) {
 144 +               kfree(tb);
 145 +               tb = NULL;
 146 +       }
 147 +#endif
 148
 149         return tb;
 150  }
 151 @@ -2139,18 +2154,31 @@ static void trie_show_stats(struct seq_f
 152
 153  #ifdef CONFIG_IP_FIB_TRIE_STATS
 154  static void trie_show_usage(struct seq_file *seq,
 155 -                           const struct trie_use_stats *stats)
 156 +                           const struct trie_use_stats __percpu *stats)
 157  {
 158 +       struct trie_use_stats s = { 0 };
 159 +       int cpu;
 160 +
 161 +       /* loop through all of the CPUs and gather up the stats */
 162 +       for_each_possible_cpu(cpu) {
 163 +               const struct trie_use_stats *pcpu = per_cpu_ptr(stats, cpu);
 164 +
 165 +               s.gets += pcpu->gets;
 166 +               s.backtrack += pcpu->backtrack;
 167 +               s.semantic_match_passed += pcpu->semantic_match_passed;
 168 +               s.semantic_match_miss += pcpu->semantic_match_miss;
 169 +               s.null_node_hit += pcpu->null_node_hit;
 170 +               s.resize_node_skipped += pcpu->resize_node_skipped;
 171 +       }
 172 +
 173         seq_printf(seq, "\nCounters:\n---------\n");
 174 -       seq_printf(seq, "gets = %u\n", stats->gets);
 175 -       seq_printf(seq, "backtracks = %u\n", stats->backtrack);
 176 +       seq_printf(seq, "gets = %u\n", s.gets);
 177 +       seq_printf(seq, "backtracks = %u\n", s.backtrack);
 178         seq_printf(seq, "semantic match passed = %u\n",
 179 -                  stats->semantic_match_passed);
 180 -       seq_printf(seq, "semantic match miss = %u\n",
 181 -                  stats->semantic_match_miss);
 182 -       seq_printf(seq, "null node hit= %u\n", stats->null_node_hit);
 183 -       seq_printf(seq, "skipped node resize = %u\n\n",
 184 -                  stats->resize_node_skipped);
 185 +                  s.semantic_match_passed);
 186 +       seq_printf(seq, "semantic match miss = %u\n", s.semantic_match_miss);
 187 +       seq_printf(seq, "null node hit= %u\n", s.null_node_hit);
 188 +       seq_printf(seq, "skipped node resize = %u\n\n", s.resize_node_skipped);
 189  }
 190  #endif /*  CONFIG_IP_FIB_TRIE_STATS */
 191
 192 @@ -2191,7 +2219,7 @@ static int fib_triestat_seq_show(struct
 193                         trie_collect_stats(t, &stat);
 194                         trie_show_stats(seq, &stat);
 195  #ifdef CONFIG_IP_FIB_TRIE_STATS
 196 -                       trie_show_usage(seq, &t->stats);
 197 +                       trie_show_usage(seq, t->stats);
 198  #endif
 199                 }
 200         }