k0kubun
commented
1 year ago Array#each
When I started working on this, rewriting Array#each resulted in increasing the number of side exits and also breaking "special variables". The following PRs are related to those issues:
- Open PRs:
- Closed PRs
The Ruby PR currently uses succ for better interpreter performance (and as a workaround for an Integer#+ override test). But since we don't have a cfunc codegen for succ yet, I'm benchmarking it with i = i.succ rewritten in i += 1.
microbenchmark
# --yjit-call-threshold=1
def bench(arr)
i = 0
arr.each do |a|
i += a
end
i
end
bench([1, 1]) # JIT
Time.now # JIT
arr = Array.new(50000000)
arr.map! { 1 }
t = Time.new
bench(arr)
p(Time.new - t)- before: 1.211382153
- after: 0.625836132
before/after is 1.94.
railsbench
master: ruby 3.3.0dev (2023-02-13T16:42:58Z master 86de48e9f6) +YJIT [x86_64-linux]
after: ruby 3.3.0dev (2023-02-13T21:49:12Z builtin-array-each 224c1f2f17) +YJIT [x86_64-linux]
---------- ----------- ---------- ---------- ---------- ------------ -------------
bench master (ms) stddev (%) after (ms) stddev (%) master/after after 1st itr
railsbench 1042.2 1.8 1046.9 1.7 1.00 0.99
---------- ----------- ---------- ---------- ---------- ------------ ---------------yjit-stats before
master (https://github.com/shopify/ruby/commit/86de48e9f6)
invokeblock exit reasons:
proc: 1,112 (59.4%)
symbol: 759 (40.6%)
leave exit reasons:
interp_return: 39,982,816 (98.0%)
start_pc_non_zero: 822,565 ( 2.0%)
se_interrupt: 400 ( 0.0%)
side_exit_count: 9,811,317
total_exit_count: 49,794,133
ratio_in_yjit: 93.1%--yjit-stats after
Rewrite Array#each in Ruby + YJIT: Consider a block ISEQ in block versioning (https://github.com/Shopify/ruby/commit/224c1f2f17 w/ i += 1 modification)
invokeblock exit reasons:
iseq_block_changed: 152,448 (98.7%)
proc: 1,264 ( 0.8%)
symbol: 759 ( 0.5%)
leave exit reasons:
interp_return: 38,833,171 (97.9%)
start_pc_non_zero: 822,559 ( 2.1%)
se_interrupt: 387 ( 0.0%)
side_exit_count: 9,914,001
total_exit_count: 48,747,172
ratio_in_yjit: 92.7%stats without "YJIT: Consider a block ISEQ in block versioning"
``` invokeblock exit reasons: iseq_block_changed: 2,158,983 (99.9%) proc: 1,264 ( 0.1%) symbol: 759 ( 0.0%) leave exit reasons: interp_return: 40,690,343 (98.0%) start_pc_non_zero: 822,559 ( 2.0%) se_interrupt: 424 ( 0.0%) side_exit_count: 11,737,658 total_exit_count: 52,428,001 ratio_in_yjit: 91.2% ```If you compare "--yjit-stats after" and "stats without YJIT: Consider a block ISEQ in block versioning", you can see https://github.com/ruby/ruby/pull/7247 contributes to significantly reducing iseq_block_changed side exits. However, it still leaves some iseq_block_changed side exits.
This reduces the amount of interp_return by 3%. Despite iseq_block_changed side exits, total_exit_count is reduced by 2% overall.
While we could still work on reducing iseq_block_changed further, it already seems like it's not going to make a significant difference in benchmarks like railsbench. The Ruby rewrite might not be useful enough until we have more optimizations unblocked by inlining, especially when liquid-render slows down on the interpreter (https://github.com/ruby/ruby/pull/6687).
cc: @maximecb
maximecb
Background
In CRuby, many methods are written in C. This contributes to the warmup speed and the performance of the interpreter, but this could sometimes be a problem for YJIT:
vm_execfor every Ruby call from C, but it also causesinterp_returnexits on leave insn.Idea
Rewrite C methods that call Ruby methods/blocks frequently in Ruby if that makes YJIT faster and doesn't slow down the interpreter too much in headline benchmarks. Past successful examples: https://github.com/ruby/ruby/pull/3281, https://github.com/ruby/ruby/pull/6983
Ones with large "block calls from C" in https://github.com/Shopify/yjit-bench/pull/168, e.g.
Array#each, might be promising targets.