performance issue about makara HOT 4 CLOSED

$ stackprof tmp/stackprof-cpu-13485-1422007173.dump --limit 10
==================================
  Mode: cpu(1000)
  Samples: 28 (17.65% miss rate)
  GC: 2 (7.14%)
==================================
     TOTAL    (pct)     SAMPLES    (pct)     FRAME
         3  (10.7%)           2   (7.1%)     ActiveRecord::LazyAttributeHash#[]
         4  (14.3%)           2   (7.1%)     block in ActiveSupport::Dependencies::Loadable#require
         2   (7.1%)           2   (7.1%)     ThreadSafe::NonConcurrentCacheBackend#[]
         1   (3.6%)           1   (3.6%)     ActiveRecord::LazyAttributeHash#assign_default_value
         1   (3.6%)           1   (3.6%)     ActiveSupport::HashWithIndifferentAccess#update
         1   (3.6%)           1   (3.6%)     ActiveModel::AttributeMethods::ClassMethods#define_proxy_call
         1   (3.6%)           1   (3.6%)     block in ActiveRecord::Result#hash_rows
         1   (3.6%)           1   (3.6%)     ActiveRecord::Relation::Merger#filter_binds
         1   (3.6%)           1   (3.6%)     <module:Associations>
         2   (7.1%)           1   (3.6%)     <module:Associations>

$ http_load -parallel 10 -seconds 10 urls.txt 
1287 fetches, 10 max parallel, 9.26704e+06 bytes, in 10 seconds
7200.5 mean bytes/connection
128.7 fetches/sec, 926704 bytes/sec
msecs/connect: 0.0838073 mean, 0.31 max, 0.032 min
msecs/first-response: 77.298 mean, 1101 max, 22.64 min
HTTP response codes:
  code 200 -- 1287

$ http_load -parallel 10 -seconds 10 urls.txt 
1295 fetches, 10 max parallel, 9.5496e+06 bytes, in 10 seconds
7374.21 mean bytes/connection
129.5 fetches/sec, 954959 bytes/sec
msecs/connect: 0.0919042 mean, 0.638 max, 0.031 min
msecs/first-response: 76.8999 mean, 1177.08 max, 20.856 min
HTTP response codes:
  code 200 -- 1295

$ stackprof tmp/stackprof-cpu-10023-1422039178.dump
==================================
  Mode: cpu(1000)
  Samples: 26 (0.00% miss rate)
  GC: 0 (0.00%)
==================================
     TOTAL    (pct)     SAMPLES    (pct)     FRAME
         2   (7.7%)           2   (7.7%)     block in ActiveSupport::Dependencies::Loadable#require
         1   (3.8%)           1   (3.8%)     <module:Associations>
         1   (3.8%)           1   (3.8%)     singleton class
         2   (7.7%)           1   (3.8%)     singleton class
         1   (3.8%)           1   (3.8%)     block (2 levels) in Net::HTTPResponse::Inflater#inflate_adapter
         1   (3.8%)           1   (3.8%)     block in Net::HTTP#connect
         1   (3.8%)           1   (3.8%)     Net::HTTP#begin_transport
         1   (3.8%)           1   (3.8%)     ActiveSupport::HashWithIndifferentAccess#default
         1   (3.8%)           1   (3.8%)     #<Module:0x007ff0c263eee8>.set_name_cache
         1   (3.8%)           1   (3.8%)     ActiveModel::AttributeMethods::ClassMethods#define_proxy_call
         1   (3.8%)           1   (3.8%)     ActiveRecord::Scoping::ScopeRegistry#raise_invalid_scope_type!
         1   (3.8%)           1   (3.8%)     <module:Associations>
         1   (3.8%)           1   (3.8%)     ActiveSupport::JSON::Encoding::JSONGemEncoder::EscapedString#to_json
         2   (7.7%)           1   (3.8%)     ActiveRecord::Reflection::AssociationReflection#association_class
         1   (3.8%)           1   (3.8%)     ActiveModel::AttributeMethods::ClassMethods#define_proxy_call
         1   (3.8%)           1   (3.8%)     block in ActiveRecord::AttributeMethods::AttributeMethodCache#[]
         1   (3.8%)           1   (3.8%)     block in ActiveRecord::DynamicMatchers::Method.match
         1   (3.8%)           1   (3.8%)     block in ActiveRecord::AttributeMethods::AttributeMethodCache#[]
         1   (3.8%)           1   (3.8%)     <module:ActiveRecord>
         1   (3.8%)           1   (3.8%)     block in Arel::Visitors::Visitor.dispatch_cache
         1   (3.8%)           1   (3.8%)     ActiveRecord::QueryMethods#where!
         1   (3.8%)           1   (3.8%)     ThreadSafe::Cache#initialize
         2   (7.7%)           1   (3.8%)     ActiveRecord::ConnectionAdapters::AbstractMysqlAdapter#configure_connection
         1   (3.8%)           1   (3.8%)     Set#include?
         4  (15.4%)           1   (3.8%)     Makara::Proxy#initialize
         1   (3.8%)           0   (0.0%)     Net::HTTP#do_start
        52 (200.0%)           0   (0.0%)     Grape::Middleware::Base#call
        26 (100.0%)           0   (0.0%)     #<Class:0x007ff0c3dd9008>#call
        26 (100.0%)           0   (0.0%)     #<Class:0x007ff0c3dd9620>#call
        26 (100.0%)           0   (0.0%)     #<Class:0x007ff0c3dd9620>#call