What's happening when initializing mruby?

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What's happening when initializing mruby? 2019-11-20 RubyConf 2019 Team Yamanekko Yurie Yamane, Masayoshi Takahashi

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Outline of this session • About us • What’s mruby • mruby demo (m5stickc) • What’s initialization • A problem of initialization • How to improve initialization • Introducing mruby-bin-nvgen • nvgen: problem and solution • Result

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About Us

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Yurie Yamane • Toppers Project member • a project of RTOS and Embedded Systems • “Talking about mruby with Matz: Today and Tomorrow” @ET2019 in this night TOPAME

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Masayoshi Takahashi • +20 Rubyist • RubyKaigi organizer team • RubyKaigi 2020 in next April, at matsumoto city

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“Introduction to mruby” • using mruby with C API • self-publishing zine in Japanese • 108 pages We are going to translate this book into English.

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What's happening when initializing mruby?

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mruby

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What’s mruby? • Lightweight implementation of Ruby • comply to ISO 30170:2012 • Used in embedded devices and in server applications • 2.1.0 will be released in this week was

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M5StickC ESP32-based 4MByte Flash, 520 KB SRAM 6-Axis IMU 0.96 inch LCD WiFi + Bluetooth 80 mAh Lipo Battery Grove Port

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M5StickC ESP32-based 4MByte Flash, 520 KB SRAM 6-Axis IMU 0.96 inch LCD WiFi + Bluetooth 80 mAh Lipo Battery Grove Port

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demo

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What's happening when initializing mruby?

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Quiz How many objects created in initialization? (1) 68 (2) 105 (3) 212 Hint: class is object

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What’s initialization “Initialization” means in this talk: == everything before executing your Ruby scripts

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What’s initialization “Initialization” means in this talk: == everything before executing your Ruby scripts •initializing mruby VM •initializing GC system •initializing all Classes and Modules •creating Object, String, Integer, Array, … •deﬁning methods for all classes / modules

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• components of VM • context • callinfo • stack • create new context • create 1 callinfo array and 1 stak on the context initializing mruby VM mruby VM (mrb_state) context … callinfo stack

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• initialize memories for Objects • ﬁxed-size memory spaces initializing GC system RVALUE (RVALUE) (RVALUE) (RVALUE) (RVALUE) (RVALUE) (RVALUE) (RVALUE) (RVALUE) (RVALUE) (RVALUE) (RVALUE) (RVALUE) (RVALUE) (RVALUE) (RVALUE) (RVALUE) (RVALUE) (RVALUE) (RVALUE)

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• create RClass (RVALUE) • create related data • methods of the class • classname • constants • create symbols initializing Class/Module Object String RClass RClass Exception RClass methods …… other data methods other data methods other data

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Problem of Initialization

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Problem of initialization • memory consumption • initialize classes, methods… • but almost all classes/modules are not changed • micro controller has small memory • mruby is (relatively) not enough to small

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How to improve it

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How to improve it • In general, ROM is wider than RAM in micro controller • RAM ROM LEGO MindStorms 64MB 16MB M5StickC 520KB 4MB SparkFun Pro nRF52840 Mini 256KB 1MB nucleo F412ZG 256KB 1024KB nucleo F411RE 128KB 512KB

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How to put data on ROM • We can’t put data on Flash ROM dynamically • because it’s ROM! • We can put them as source code in C • use keyword const • pre-execution and code generation const struct RClass nv_object_212 = { .tt=MRB_TT_CLASS, .color=7, .ﬂags=212, .c=(struct RClass *)&nv_object_211, .gcnext= (struct RBasic*)&nv_object_210, .iv=(struct iv_tbl*)&nv_iv_90, .mt=(struct kh_mt*)&nv_mt_86_empty, .super =NULL, /* name=BasicObject */ };

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pre-execution A = Array.new A << 1 if A.size >= 1 A += [2, 3] end A = [1, 2, 3] pre- execution original generated

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e code generation generator and executable • generator generates *.c ﬁles • symbols • objects • … • put on ROM and RAM • executable is build with *.c, *.rb and mruby core mruby core symbol table (presym.c) objects, method tables, strings, … (generated.c) generator mruby core app.rb executable

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nvgen

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nvgen • Non-Volatile mruby Generator (mruby-bin-nvgen) • a mrbgem of (modiﬁed) mruby • generate Symbol tables (presym.c), objects and related data structures (generated.c) • C structures generated via mrb_open() mruby core symbol table (presym.c) objects, method tables, strings, … (generated.c) nvgen

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nvgen • new app consists of mruby core and generated ﬁles (presym.c and generated.c) mruby core symbol table (presym.c) objects, method tables, strings, … (generated.c) new app (executable)

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memory map • ROM • RODATA • RAM • DATA • global variables in C • HEAP • allocated dynamically • STACK • call stack in C • sharing area with HEAP RODATA DATA HEAP STACK

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memory usage of nvgen 30%"5" 30. %"5" 3". )&"1 3". 0CKFDU 37"-6& NFUIPEUBCMF BEEFE NSC@TUBUF 4ZNCPM*% OBNF *7UBCMF TUBDL NFUIPEUBCMF EFpOFE DPOUFYU 4ZNCPM BEEFE *3&1 qBHT<> 0CKFDU BEEFE TUBDL PSJH NFUIPET BEEFE NSC@TUBUF PSJH JTFR<>

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without nvgen class mrb_state iv_tbl internal data mt methods HEAP

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with nvgen class mrb_state iv_tbl internal data methods ROM mt HEAP DATA ﬂags

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with nvgen: add methods class mrb_state iv_tbl internal data methods ROM mt methods HEAP DATA ﬂags

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with nvgen: add class class mrb_state iv_tbl internal data methods ROM mt methods HEAP DATA class ﬂags

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with nvgen: new objects class mrb_state iv_tbl internal data methods ROM mt methods HEAP DATA class object ﬂags

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algorythm of nvgen collect objects scan information to dump dump symbols dump objects and methods dump mruby VM (mrb_state, callinfos, stack)

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mruby’s objects in C mrb_value mrb_value Integer, Symbol Object, Class RVALUE String mrb_value RVALUE char[] Array mrb_value RVALUE mrb_value[]

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mrb_value • TT + mrb_int • Integer • TT + mrb_sym • Symbol • TT + pointer • Other Classes • TT: Type Tag; type of value (0-24) TT void *p (32bit pointer) mrb_int (32bit int) mrb_sym (32bit uint) mrb_value TT TT Symbol Fixnum Other

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RVALUE • common items: MRB_OBJECT_HEADER • class-speciﬁc items ex) RClass • common object header • pointer to instance variables • pointer to method table • pointer to super class MRB_OBJECT_HEADER *iv (instance variables) *mt (method table) *super (super class) RClass

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RVALUE class Foo def initialize(name) @name = name end def say puts “#{@name}!!” end end foo = Foo.new MRB_OBJECT_HEADER class Foo •initialize •say class Object mt super iv

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Method structure • struct RProc (RVALUE) • method deﬁned in C • pointer to C function • method deﬁned in Ruby • compiled as bytecode • IREP (mrb_irep) structure • IREP can be nested RProc irep RProc c function in C in Ruby irep irep

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def hello(name) puts name end hello("Hello!") IREP data structure of code (method / block)

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def hello(name) puts name end hello("Hello!") IREP irep irep data structure of code (method / block)

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def hello(name) puts name end hello("Hello!") IREP • nlocals (num. of local variables) • nregs (num. of registers) • ISEQ (bytecode) • pools • symbols • reps (pointer to IREPs) • rlen (num. of sub IREPs) • … data structure of code (method / block) irep irep

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IREP (mrbc) irep 0x7fe595c0cb20 nregs=4 nlocals=1 pools=1 syms=1 reps=1 iseq=20 ﬁle: hello.rb 1 000 OP_TCLASS R1 1 002 OP_METHOD R2 I(0:0x7fe595c0cdd0) 1 005 OP_DEF R1 :hello 5 008 OP_LOADSELF R1 5 010 OP_STRING R2 L(0) ; "Hello!" 5 013 OP_SEND R1 :hello 1 5 017 OP_RETURN R1 5 019 OP_STOP irep 0x7fe595c0cdd0 nregs=6 nlocals=3 pools=0 syms=1 reps=0 iseq=15 local variable names: R1:name R2:& ﬁle: hello.rb 1 000 OP_ENTER 1:0:0:0:0:0:0 2 004 OP_LOADSELF R3 2 006 OP_MOVE R4 R1 ; R1:name 2 009 OP_SEND R3 :puts 1 2 013 OP_RETURN R3 def hello(name) puts name end hello("Hello!")

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problem and solution of nvgen

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flags of objects • obj->flags is used as status of objects • flags should be mutable • So an array of flags for ROM’s objects are located in RAM • add macro to read and write them • obj->flags in ROM are indexes of the array flags flags flags flags flags flags … ROM RAM

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GC with RAM and ROM • mruby uses tri-color GC (Black, White, Gray) • We use quad-color GC, add Red • Red are never GCed; objects in ROM are Red • At first of GC cycle, all children of Red objects are marked • VM has a list of Red objects ROM RAM

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methods with RAM and ROM • method tables are in both ROM and RAM • tables for pre-defined methods are in ROM • using iv_tbl to store pointer of pre-defined method tables • key is __mt2__, which is not used as instance variables new methods pre-deﬁned methods __mt2__ *mt *iv_tbl

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Demo

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IoT Demo • Sensor • 6-axis motion sensor • Network • WiFi • Protocol • MQTT publish sensor data to server Server sensor Device MQTT

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Motion Sensor • X • Y • Z • Roll • Pitch • Yaw MPU-6886 6 axis motion sensor (IMU) Device Z Y X Pitch Roll Yaw sensor

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aws_iot.rb accx, accy, accz = mpu.accel_data pitch, roll, yaw = mpu.gyro_data temp = mpu.temp_data t = M5StickC::Time.now LCD.printf("ah pitch:%2.2f roll:%2.2f, yaw:%2.2f\n", pitch, roll, yaw) message = sprintf(‘{"timestamp":"%s","gyroX": %2.2f,"gyroY": %2.2f,"gyroZ": %2.2f,"accX": %. 2f,"accY": %.2f,"accZ": %.2f,"temp": %.2f}', t.xmlschema, pitch, roll, yaw, accx * 1000, accy * 1000, accz * 1000, temp) aws.publish(pub_topic, message)

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IoT Demo • AWS IoT • MQTT Broker • Elasticsearch • collect and analyze data from AWS IoT • Kibana • visualize on dashboard publish sensor data to server AWS IoT Elasticseaerch Device Kibana

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Let's try!

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Benchmark

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EFGBVMU /7

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Future Works

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Future Work • support 2.1.0 • feedback to mruby/mruby • make available without modiﬁcation of mruby

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Special Thanks to: • The Ruby Association • This work is supported Ruby Association grant program in 2018 • The mruby forum • Aaron Patterson @tenderlove • Kishimaworks