Feature #20011
closedReduce implicit array allocations on caller side of method calling
Description
I would like to use the peephole optimizer to eliminate caller-side array allocations for the following cases, by switching splatarray true
to splatarray false
:
f(1, *a)
f(1, *a, &lvar)
f(1, *a, &@ivar)
f(*a, **lvar)
f(*a, **@ivar)
f(*a, **lvar, &lvar)
f(*a, **@ivar, &@ivar)
f(*a, kw: 1)
f(*a, kw:1, &lvar)
f(*a, kw:1, &@ivar)
In terms of safety, currently, f(*a, &lvar)
and f(*a, &@ivar)
both avoid array allocations (splatarray false
), and all of the above are as safe as those in terms of safety. Note that since at least Ruby 1.8, in pathlogical cases, lvar.to_proc
can modify a
, which results in behavior contrary to expected evaluation order:
ary = [1,2]
kwd = Object.new
kwd.define_singleton_method(:to_proc) {ary << 4; lambda{}}
p(*ary, &kwd)
# 4 included in output
I think that for both the current f(*a, &lvar)
and f(*a, &@ivar)
cases and all of the above cases, the benefit of avoiding the allocation is higher than the costs, considering that only pathologic cases fail. If we do not want the above optimization, for consistency, we should remove the optimization of f(*a, &lvar)
and f(*a, &@ivar)
(or update the optimization so that it is only used if lvar
or @ivar
is already a proc), which will slow Ruby down.
I have submitted a pull request for these changes: https://github.com/ruby/ruby/pull/8853
To make sure these cases are worth optimizing, I did some analysis:
For ruby -e '' (just loads rubygems):
5 : f(1, *a)
2 : f(1, *a, &lvar) | f(1, *a, &@ivar)
Current stdlib:
139 : f(1, *a)
3 : f(1, *a, &lvar) | f(1, *a, &@ivar)
4 : f(*a, **lvar) | f(*a, **@ivar)
Rails master:
77 : f(1, *a)
5 : f(1, *a, &lvar) | f(1, *a, &@ivar)
26 : f(*a, **lvar) | f(*a, **@ivar)
5 : f(*a, kw: 1)
minitest 5.20 (bundled gem):
4 : f(1, *a)
1 : f(1, *a, &lvar) | f(1, *a, &@ivar)
2 : f(*a, **lvar) | f(*a, **@ivar)
2 : f(*a, **lvar, &lvar) | f(*a, **@ivar, &@ivar)
capybara 3.39.2:
15 : f(1, *a)
2 : f(1, *a, &lvar) | f(1, *a, &@ivar)
19 : f(*a, **lvar) | f(*a, **@ivar)
4 : f(*a, **lvar, &lvar) | f(*a, **@ivar, &@ivar)
This shows that all cases optimized except f(*a, kw:1, &lvar)
and f(*a, kw:1, &@ivar)
are used in common gems. Those cases could be removed if people think they are not worth optimizing.
Code backing the above analysis can be found at https://github.com/ruby/ruby/pull/8853#issuecomment-1817656139
Updated by byroot (Jean Boussier) 9 months ago
I tried this on Shopify's monolith CI and it's breaking quite hard:
ATTRIBUTE_NAMES = T.let(
[
:currency,
:description,
:kind,
:price,
:reasons,
:receipt,
:shipping_service_charge_id,
:shipping_service_label_id,
:origin_address,
].freeze,
T::Array[Symbol]
)
T.unsafe(self).validates(*ATTRIBUTE_NAMES, presence: true) # here
`<class:Payload>': can't modify frozen Array: [:currency, :description, :kind, :price, :reasons, :receipt, :shipping_service_charge_id, :shipping_service_label_id, :origin_address] (FrozenError)
from /app/components/delivery/app/services/shipping/adjustment_creator/payload.rb:6:in `<class:AdjustmentCreator>'
from /app/components/delivery/app/services/shipping/adjustment_creator/payload.rb:5:in `<module:Shipping>'
from /app/components/delivery/app/services/shipping/adjustment_creator/payload.rb:4:in `<main>'
(I originally reported this on the wrong issue)
Updated by jeremyevans0 (Jeremy Evans) 9 months ago
byroot (Jean Boussier) wrote in #note-1:
I tried this on Shopify's monolith CI and it's breaking quite hard:
Thanks for testing. I think I found and fixed the issue: https://github.com/ruby/ruby/pull/8853/commits/d9a6f7a77ab5d682950f891990401a95f8fdc6f0
Can you test and see if that fixes it, or if there is another issue?
Updated by byroot (Jean Boussier) 9 months ago
@jeremyevans0 (Jeremy Evans) Looks good now!
Updated by ko1 (Koichi Sasada) 9 months ago
Could you provide benchmarks?
Updated by jeremyevans0 (Jeremy Evans) 9 months ago
ko1 (Koichi Sasada) wrote in #note-4:
Could you provide benchmarks?
I added a benchmark to the pull request. Here are the results:
arg_splat
after-patch: 11633482.8 i/s
before-patch: 6603689.5 i/s - 1.76x slower
arg_splat_block
after-patch: 10011285.1 i/s
before-patch: 6072490.8 i/s - 1.65x slower
splat_kw_splat
after-patch: 5574867.8 i/s
before-patch: 4025629.4 i/s - 1.38x slower
splat_kw_splat_block
after-patch: 4977728.5 i/s
before-patch: 3827400.9 i/s - 1.30x slower
splat_kw
after-patch: 3686117.6 i/s
before-patch: 3103409.3 i/s - 1.19x slower
splat_kw_block
after-patch: 3535774.1 i/s
before-patch: 2957890.6 i/s - 1.20x slower
So a 20%-75% increase in performance depending on the type of method call.
Updated by jeremyevans0 (Jeremy Evans) 9 months ago
I expanded the pull request to handle getblockparamproxy
for block arguments, in addition to getlocal
and getinstancevariable
. getblockparamproxy
is used inside methods, when the block being passed in the current calls was passed as the block to the current method. This expanded the number of cases optimized:
stdlib:
144 : f(1, *a)
5 : f(1, *a, &lvar) | f(1, *a, &@ivar)
4 : f(*a, **lvar) | f(*a, **@ivar)
3 : f(*a, **lvar, &lvar) | f(*a, **@ivar, &@ivar)
Rails master lib:
82 : f(1, *a)
7 : f(1, *a, &lvar) | f(1, *a, &@ivar)
26 : f(*a, **lvar) | f(*a, **@ivar)
6 : f(*a, **lvar, &lvar) | f(*a, **@ivar, &@ivar)
5 : f(*a, kw: 1)
minitest 5.20 (bundled gem):
9 : f(1, *a)
3 : f(1, *a, &lvar) | f(1, *a, &@ivar)
2 : f(*a, **lvar) | f(*a, **@ivar)
4 : f(*a, **lvar, &lvar) | f(*a, **@ivar, &@ivar)
capybara 3.39.2:
20 : f(1, *a)
4 : f(1, *a, &lvar) | f(1, *a, &@ivar)
19 : f(*a, **lvar) | f(*a, **@ivar)
14 : f(*a, **lvar, &lvar) | f(*a, **@ivar, &@ivar)
Updated by ko1 (Koichi Sasada) 8 months ago
Thank you. Please try it.