patch nuke-the-dbuf-hash

*** 498,588 ****
              db.db_holds.rc_count, path);
  
          return (DCMD_OK);
  }
  
- /* ARGSUSED */
- static int
- dbuf_stats(uintptr_t addr, uint_t flags, int argc, const mdb_arg_t *argv)
- {
- #define HISTOSZ 32
-         uintptr_t dbp;
-         dmu_buf_impl_t db;
-         dbuf_hash_table_t ht;
-         uint64_t bucket, ndbufs;
-         uint64_t histo[HISTOSZ];
-         uint64_t histo2[HISTOSZ];
-         int i, maxidx;
- 
-         if (mdb_readvar(&ht, "dbuf_hash_table") == -1) {
-                 mdb_warn("failed to read 'dbuf_hash_table'");
-                 return (DCMD_ERR);
-         }
- 
-         for (i = 0; i < HISTOSZ; i++) {
-                 histo[i] = 0;
-                 histo2[i] = 0;
-         }
- 
-         ndbufs = 0;
-         for (bucket = 0; bucket < ht.hash_table_mask+1; bucket++) {
-                 int len;
- 
-                 if (mdb_vread(&dbp, sizeof (void *),
-                     (uintptr_t)(ht.hash_table+bucket)) == -1) {
-                         mdb_warn("failed to read hash bucket %u at %p",
-                             bucket, ht.hash_table+bucket);
-                         return (DCMD_ERR);
-                 }
- 
-                 len = 0;
-                 while (dbp != 0) {
-                         if (mdb_vread(&db, sizeof (dmu_buf_impl_t),
-                             dbp) == -1) {
-                                 mdb_warn("failed to read dbuf at %p", dbp);
-                                 return (DCMD_ERR);
-                         }
-                         dbp = (uintptr_t)db.db_hash_next;
-                         for (i = MIN(len, HISTOSZ - 1); i >= 0; i--)
-                                 histo2[i]++;
-                         len++;
-                         ndbufs++;
-                 }
- 
-                 if (len >= HISTOSZ)
-                         len = HISTOSZ-1;
-                 histo[len]++;
-         }
- 
-         mdb_printf("hash table has %llu buckets, %llu dbufs "
-             "(avg %llu buckets/dbuf)\n",
-             ht.hash_table_mask+1, ndbufs,
-             (ht.hash_table_mask+1)/ndbufs);
- 
-         mdb_printf("\n");
-         maxidx = 0;
-         for (i = 0; i < HISTOSZ; i++)
-                 if (histo[i] > 0)
-                         maxidx = i;
-         mdb_printf("hash chain length   number of buckets\n");
-         for (i = 0; i <= maxidx; i++)
-                 mdb_printf("%u                  %llu\n", i, histo[i]);
- 
-         mdb_printf("\n");
-         maxidx = 0;
-         for (i = 0; i < HISTOSZ; i++)
-                 if (histo2[i] > 0)
-                         maxidx = i;
-         mdb_printf("hash chain depth    number of dbufs\n");
-         for (i = 0; i <= maxidx; i++)
-                 mdb_printf("%u or more          %llu    %llu%%\n",
-                     i, histo2[i], histo2[i]*100/ndbufs);
- 
- 
-         return (DCMD_OK);
- }
- 
  #define CHAIN_END 0xffff
  /*
   * ::zap_leaf [-v]
   *
   * Print a zap_leaf_phys_t, assumed to be 16k
--- 498,507 ----
*** 3268,3278 ****
  
  static const mdb_dcmd_t dcmds[] = {
          { "arc", "[-bkmg]", "print ARC variables", arc_print },
          { "blkptr", ":", "print blkptr_t", blkptr },
          { "dbuf", ":", "print dmu_buf_impl_t", dbuf },
-         { "dbuf_stats", ":", "dbuf stats", dbuf_stats },
          { "dbufs",
              "\t[-O objset_t*] [-n objset_name | \"mos\"] "
              "[-o object | \"mdn\"] \n"
              "\t[-l level] [-b blkid | \"bonus\"]",
              "find dmu_buf_impl_t's that match specified criteria", dbufs },
--- 3187,3196 ----