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Improving CVAR
performance in
Ruby 3.1
EILEEN M. UCHITELLE | @eileencodes
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Thank You RubyConf
organizers, staff, &
attendees —
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Eileen M. Uchitelle
@eileencodes
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Core Team
Member
of Ruby on Rails
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f Principal Software
Engineer
at GitHub
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Improving CVAR
performance in
Ruby 3.1
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What is a CVAR?
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What is a CVAR?
class MyClass
@@cvar = 1
def self.read_cvar
@@cvar
end
end
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What is a CVAR?
class MyClass
@@cvar = 1
def self.read_cvar
@@cvar
end
end
Writer
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What is a CVAR?
class MyClass
@@cvar = 1
def self.read_cvar
@@cvar
end
end
Reader
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How does CVAR
inheritance work?
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IVAR inheritance
class Dog
attr_reader :name, :owner
def initialize
@name = "Arya"
@owner = "Eileen"
end
end
class Puppy < Dog
def initialize
@name = "Sansa"
end
end
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IVAR inheritance
> Dog.new.name
=> "Arya"
> Dog.new.owner
=> "Eileen"
> Puppy.new.name
=> "Sansa"
> Puppy.new.owner
=> nil
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CVAR inheritance
class Dog
@@name = "Arya"
@@owner = "Eileen"
def self.name
@@name
end
def self.owner
@@owner
end
end
class Puppy < Dog
@@name = "Sansa"
end
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CVAR inheritance
> Dog.owner
=> "Eileen"
> Puppy.owner
=> "Eileen"
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CVAR inheritance
> Dog.owner
=> "Eileen"
> Puppy.owner
=> "Eileen"
> Dog.name
=> "Sansa"
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CVAR inheritance
> Dog.owner
=> "Eileen"
> Puppy.owner
=> "Eileen"
> Dog.name
=> "Sansa"
> Puppy.name
=> "Sansa"
🤔
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Puppy
Object
Dog
Kernel
BasicObject
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Puppy
Dog
Object
Kernel
BasicObject
Stores
@@name
@@owner
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@@name "Sansa"
RCLASS_IV_TBL
Puppy
Dog
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Understanding CVAR
Overtaken
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CVAR Overtaken
class Dog
end
class Puppy < Dog
@@name = "Sansa"
def self.name
@@name
end
end
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CVAR Overtaken
class Dog
end
class Puppy < Dog
@@name = "Sansa"
def self.name
@@name
end
end
class Dog
@@name = "Arya"
end
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CVAR Overtaken
> Puppy.name
=> class variable @@name of Puppy is overtaken
by Dog
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The deeper the
inheritance chain the
slower CVAR access is
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CVAR Benchmarks
MODULES = ["A", ..."WWWW"]
class One
@@cvar = 1
def self.cvar
@@cvar
end
eval <<-EOM
module #{MODULES.first}
end
include #{MODULES.first}
EOM
end
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CVAR Benchmarks
class Thirty
@@cvar = 1
def self.cvar
@@cvar
end
MODULES.take(30).each do |module_name|
eval <<-EOM
module #{module_name}
end
include #{module_name}
EOM
end
end
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CVAR Benchmarks
class OneHundred
@@cvar = 1
def self.cvar
@@cvar
end
MODULES.each do |module_name|
eval <<-EOM
module #{module_name}
end
include #{module_name}
EOM
end
end
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CVAR Benchmarks
Benchmark.ips do |x|
x.report "1 module" do
One.cvar
end
x.report "30 modules" do
Thirty.cvar
end
x.report "100 modules" do
OneHundred.cvar
end
x.compare!
end
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CVAR Benchmarks
Warming up --------------------------------------
1 module 1.231M i/100ms
30 modules 432.020k i/100ms
100 modules 145.399k i/100ms
Calculating -------------------------------------
1 module 12.210M (± 2.1%) i/s - 61.553M in 5.043400s
30 modules 4.354M (± 2.7%) i/s - 22.033M in 5.063839s
100 modules 1.434M (± 2.9%) i/s - 7.270M in 5.072531s
Comparison:
1 module: 12209958.3 i/s
30 modules: 4354217.8 i/s - 2.80x (± 0.00) slower
100 modules: 1434447.3 i/s - 8.51x (± 0.00) slower
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S
CVAR Benchmarks
Warming up --------------------------------------
1 module 1.231M i/100ms
30 modules 432.020k i/100ms
100 modules 145.399k i/100ms
Calculating -------------------------------------
1 module 12.210M (± 2.1%) i/s - 61.553M in 5.043400s
30 modules 4.354M (± 2.7%) i/s - 22.033M in 5.063839s
100 modules 1.434M (± 2.9%) i/s - 7.270M in 5.072531s
Comparison:
1 module: 12209958.3 i/s
30 modules: 4354217.8 i/s - 2.80x (± 0.00) slower
100 modules: 1434447.3 i/s - 8.51x (± 0.00) slower 8.5x!
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Are CVARs really that
common?
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CVARs in Rails
module ActiveRecord
module Core
def self.configurations=(config)
@@configurations = ActiveRecord::DatabaseConfigs.new(config)
end
self.configurations = {}
def self.configurations
@@configurations
end
end
end
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CVARs in Rails
module ActiveRecord
module Core
mattr_accessor :logger, instance_writer: false
mattr_accessor :verbose_query_logs, instance_writer: false, default: false
mattr_accessor :schema_format, instance_writer: false, default: :ruby
mattr_accessor :dump_schemas, instance_writer: false, default: :schema_search_path
mattr_accessor :dump_schema_after_migration, instance_writer: false, default: true
end
end
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CVARs in Rails
> ActiveRecord::Base.ancestors.count
=> 73
> ActionController::Base.ancestors.count
=> 71
> ActiveJob.ancestors.count
=> 29
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Building a cache for
CVARs
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No content
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@@name "Sansa"
RCLASS_IV_TBL RCLASS_CVC_TBL
Dog
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@@name "Sansa"
RCLASS_IV_TBL
@@name
RCLASS_CVC_TBL
Dog
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@@name "Sansa"
RCLASS_IV_TBL
@@name Inline cache
RCLASS_CVC_TBL
Dog
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@@name "Sansa"
RCLASS_IV_TBL
@@name Inline cache
RCLASS_CVC_TBL
Dog pointer
global_cvar_state
Dog
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@@name "Sansa"
RCLASS_IV_TBL
@@name Inline cache
RCLASS_CVC_TBL
Dog pointer
global_cvar_state
Dog
Puppy
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Puppy.name
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Puppy.name
global_cvar_state == GET_GLOBAL_CVAR_STATE()
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Puppy.name
Dog
global_cvar_state == GET_GLOBAL_CVAR_STATE()
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Dog
Puppy.name
global_cvar_state == GET_GLOBAL_CVAR_STATE()
@@name "Sansa"
RCLASS_IV_TBL
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S
CVAR Cache PR
github.com/ruby/ruby/pull/4340
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Benchmarking
performance
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S
CVAR Benchmarks
Warming up --------------------------------------
1 module 1.231M i/100ms
30 modules 432.020k i/100ms
100 modules 145.399k i/100ms
Calculating -------------------------------------
1 module 12.210M (± 2.1%) i/s - 61.553M in 5.043400s
30 modules 4.354M (± 2.7%) i/s - 22.033M in 5.063839s
100 modules 1.434M (± 2.9%) i/s - 7.270M in 5.072531s
Comparison:
1 module: 12209958.3 i/s
30 modules: 4354217.8 i/s - 2.80x (± 0.00) slower
100 modules: 1434447.3 i/s - 8.51x (± 0.00) slower 8.5x!
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S
CVAR Benchmarks
Warming up --------------------------------------
1 module 1.641M i/100ms
30 modules 1.655M i/100ms
100 modules 1.620M i/100ms
Calculating -------------------------------------
1 module 16.279M (± 3.8%) i/s - 82.038M in 5.046923s
30 modules 15.891M (± 3.9%) i/s - 79.459M in 5.007958s
100 modules 16.087M (± 3.6%) i/s - 81.005M in 5.041931s
Comparison:
1 module: 16279458.0 i/s
100 modules: 16087484.6 i/s
30 modules: 15891406.2 i/s
No difference!
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S
CVAR Benchmarks
$ RAILS_ENV=production INTERVAL=100 WARMUP=1 BENCHMARK=10000 ruby bin/bench
ruby 3.1.0dev (2021-06-04T00:24:57Z master 91c542ad05) [x86_64-darwin19]
Warming up...
Warmup: 1 requests
Benchmark: 10000 requests
Request per second: 615.1 [#/s] (mean)
Percentage of the requests served within a certain time (ms)
50% 1.57
66% 1.68
75% 1.74
80% 1.78
90% 1.91
95% 2.06
98% 2.36
99% 2.67
100% 35.15
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S
CVAR Benchmarks
$ RAILS_ENV=production INTERVAL=100 WARMUP=1 BENCHMARK=10000 ruby bin/bench
ruby 3.1.0dev (2021-06-04T17:40:20Z add-cache-for.. 37c96af98b) [x86_64-darwin19]
Warming up...
Warmup: 1 requests
Benchmark: 10000 requests
Request per second: 657.1 [#/s] (mean)
Percentage of the requests served within a certain time (ms)
50% 1.46
66% 1.56
75% 1.63
80% 1.68
90% 1.82
95% 2.01
98% 2.28
99% 2.50
100% 35.13
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What did we
learn?
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🐞!
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S
Feature Request
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Every OSS change
has tradeoffs
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Every OSS change
has tradeoffs
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Tradeoffs
Increased complexity
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Tradeoffs
Encourages more usage
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Tradeoffs
Increased maintenance
burden
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Every OSS change
is a negotiation
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Negotiation
CVARs aren't going
anywhere
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Negotiation
Demonstrate real-world
improvements
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Negotiation
Improve all applications by
upgrading
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Let's do more of this
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Let's do more of this
By learning C
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Let's do more of this
By reading "Ruby Under a
Microscope"
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Let's do more of this
By making small changes
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Making Ruby better
benefits everyone
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Making Ruby better
benefits you
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Let's go make Ruby
better, together
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Thank You RubyConf!
EILEEN M. UCHITELLE | @eileencodes