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Elixir を⽀える技術 -「落ちない」システムの秘密に迫る
Elixir: Under the Hood
Takanori Ishikawa / builderscon tokyo 2019
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Elixir: Under the Hood
Elixir を⽀える技術 -「落ちない」システムの秘密に迫る
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• @takanori_is
• Takanori Ishikawa
• ABEJA, inc.
• Ex) mixi, Drecom
• Developer in ABEJA Platform
• ❤ Elixir and
• https://github.com/ishikawa
• Born in 愛媛県松⼭市
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Summary
• Erlang & Elixir design and principal
• Systems that run forever
• BEAM internal
• Optimizations for BEAM
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Erlang
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History of Erlang
• 1982 - 1985: Experiments using > 20 different languages
• 1985 - 86: Experiments with Lisp,Prolog, Parlog
• 1987: Erlang
• 1993: Distribution
• 1998: Open Sourced
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Copyright © ABEJA, Inc. All rights reserved. https://medium.com/elixirlabs/anatomy-of-an-elixir-process-878030c37166
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Elixir
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Elixir Design Goals
• Compatibility
• the Erlang VM is Elixir’s strongest asset
• Productivity
• Extensibility
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Copyright © ABEJA, Inc. All rights reserved. https://blog.stenmans.org/theBeamBook/#ERTS
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「落ちないシステム」
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「100% バグがないシステムを
作れば落ちない！」
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Systems run forever
• Process Isolation
• Fault tolerance
• Self healing
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The Erlang Virtual Machine:
BEAM
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The Erlang Virtual Machine: BEAM
• BEAM (Bogumil’s/Björn’s Abstract Machine)
• garbage collecting
• reduction counting
• non-preemptive
• Interpreter loop: directly threaded
• register machine
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Process
• Heap
• Stack
• Mailbox
• PCB (Process Control Block)
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https://hamidreza-s.github.io/erlang/scheduling/real-time/preemptive/migration/2016/02/09/erlang-scheduler-
details.html
Erlang VM
+--------------------------------------------------------+
| |
| +-----------------+-----------------+ |
| | | | |
| | Scheduler # 1 | Run Queue # 1 <--+ |
| | | | | |
| +-----------------+-----------------+ | |
| | |
| +-----------------+-----------------+ | |
| | | | | |
| | Scheduler # 2 | Run Queue # 2 <----> Migration |
| | | | | Logic |
| +-----------------+-----------------+ | |
| | |
| +-----------------+-----------------+ | |
| | | | | |
| | Scheduler # N | Run Queue # N <--+ |
| | | | |
| +-----------------+-----------------+ |
| |
+--------------------------------------------------------+
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Copyright © ABEJA, Inc. All rights reserved. https://www.erlang-solutions.com/blog/erlang-garbage-collector.html
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Optimization
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HiPE
• High Performance Erlang
• Native code compiler for Erlang
• Including LLVM backend
• Compiles individual Erlang functions
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BEAMJIT
• Since 2014
• Tracing JIT
• LLVM backend
• Future:
• BEAM registers to machine registers
• Cross trace optimizations
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BEAM improvements
• Interpreter Overhaul
• Instruction size reduced
• New IR: SSA based
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SSA
• SSA (Static Single Assignment)
• Each variable is assigned exactly once,
• and every variable is defined before it is used.
• @variable:5
• Simplifies compiler optimizations
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Conclusion
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Summary
• Erlang & Elixir design and principal
• Systems that run forever
• BEAM internal
• Optimizations for BEAM
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Thanks!