Project

General

Profile

Actions
Copy link

Misc #16160

open

Lazy init thread local storage

Misc #16160: Lazy init thread local storage

Added by methodmissing (Lourens Naudé) about 6 years ago. Updated about 6 years ago.

Status:
Open
Assignee:
-
[ruby-core:94876]

Description

References PR https://github.com/ruby/ruby/pull/2295

Why?

The local_storage member of execution context is lazy initialized and drives the Thread#[] and Thread#[]= APIs, which are Fiber local and not Thread local storage. I think the same lazy init pattern should be applied to the APIs below as well - reduces one Hash alloc per thread created that does not use thread locals.

Lazy allocates thread local storage for the following APIs

  • Thread#thread_variable_get - early returns nil on locals Hash not initialised
  • Thread#thread_variable_set - forces allocation of the locals Hash if not initilalised
  • Thread#thread_variables - early returns the empty array AND saves on Hash iteration if locals Hash not initialised
  • Thread#thread_variable? - early returns false on locals Hash not initialised

Other notes

  • Moved initial implementation from internal.h to thread.c local to call sites.
  • Preferred defs/id.def for the locals ID (seeing this pattern used more often, but not sure if that is preferred to inline rb_intern yet. Either way there's quite a few different conventions around IDs in the codebase at the moment and happy to help converging to a standard instead.
  • Maybe a flag is overkill and NIL_P on locals ivar could also work ...

Thoughts?

Updated by nobu (Nobuyoshi Nakada) about 6 years ago Actions
Copy link
 #1 [ruby-core:94977]

I'm positive about this, except for the performance.
Do you have any numbers?

Updated by methodmissing (Lourens Naudé) about 6 years ago Actions
Copy link
 #2 [ruby-core:95028]

nobu (Nobuyoshi Nakada) wrote:

I'm positive about this, except for the performance.
Do you have any numbers?

Apologies for the delay in replying.

Using benchmark-driver script (running set last as it would taint the others by initializing the locals table on the thread object initialized in prelude):

prelude: | th = Thread.new {} benchmark: thread_variable_get: th.thread_variable_get('foo') thread_variables: th.thread_variables thread_variable_p: th.thread_variable?('foo') thread_variable_set: th.thread_variable_set('foo', 'bar') loop_count: 1000000 
lourens@CarbonX1:~/src/ruby/ruby$ /usr/local/bin/ruby --disable=gems -rrubygems -I./benchmark/lib ./benchmark/benchmark-driver/exe/benchmark-driver --executables="compare-ruby::~/src/ruby/trunk/ruby --disable=gems -I.ext/common --disable-gem" --executables="built-ruby::./miniruby -I./lib -I. -I.ext/common -r./prelude --disable-gem" -v --repeat-count=10 $HOME/src/lazy_init_thread_locals.yml compare-ruby: ruby 2.7.0dev (2019-09-22T01:11:51Z master a0ce0b6297) [x86_64-linux] built-ruby: ruby 2.7.0dev (2019-09-22T01:21:06Z lazy-init-thread-l.. 24463b7252) [x86_64-linux] Calculating ------------------------------------- compare-ruby built-ruby thread_variable_get 11.305M 33.901M i/s - 1.000M times in 0.088456s 0.029498s thread_variables 22.765M 40.344M i/s - 1.000M times in 0.043927s 0.024787s thread_variable_p 19.260M 20.883M i/s - 1.000M times in 0.051921s 0.047886s thread_variable_set 8.195M 8.543M i/s - 1.000M times in 0.122030s 0.117054s Comparison: thread_variable_get built-ruby: 33900806.8 i/s compare-ruby: 11305022.7 i/s - 3.00x slower thread_variables built-ruby: 40344251.1 i/s compare-ruby: 22765106.8 i/s - 1.77x slower thread_variable_p built-ruby: 20882884.5 i/s compare-ruby: 19260142.8 i/s - 1.08x slower thread_variable_set built-ruby: 8543090.8 i/s compare-ruby: 8194725.4 i/s - 1.04x slower

A regression on thread_variable_set, but improvement on others.

And with memory runner (although knowing ahead of time it's just the hash, 40 bytes with array table saved):

lourens@CarbonX1:~/src/ruby/ruby$ /usr/local/bin/ruby --disable=gems -rrubygems -I./benchmark/lib ./benchmark/benchmark-driver/exe/benchmark-driver --executables="compare-ruby::~/src/ruby/trunk/ruby --disable=gems -I.ext/common --disable-gem" --executables="built-ruby::./miniruby -I./lib -I. -I.ext/common -r./prelude --disable-gem" -v --repeat-count=10 -r memory $HOME/src/lazy_init_thread_locals.yml compare-ruby: ruby 2.7.0dev (2019-09-22T01:11:51Z master a0ce0b6297) [x86_64-linux] built-ruby: ruby 2.7.0dev (2019-09-22T01:21:06Z lazy-init-thread-l.. 24463b7252) [x86_64-linux] Calculating ------------------------------------- compare-ruby built-ruby thread_variable_get 11.632M 11.528M bytes - 1.000M times thread_variables 11.668M 11.472M bytes - 1.000M times thread_variable_p 11.692M 11.452M bytes - 1.000M times thread_variable_set 11.652M 11.568M bytes - 1.000M times Comparison: thread_variable_get built-ruby: 11528000.0 bytes compare-ruby: 11632000.0 bytes - 1.01x larger thread_variables built-ruby: 11472000.0 bytes compare-ruby: 11668000.0 bytes - 1.02x larger thread_variable_p built-ruby: 11452000.0 bytes compare-ruby: 11692000.0 bytes - 1.02x larger thread_variable_set built-ruby: 11568000.0 bytes compare-ruby: 11652000.0 bytes - 1.01x larger
Actions
Copy link

Also available in: PDF Atom