From 5bb1d4d288d019e276335465d0389fd2f5246bfd Mon Sep 17 00:00:00 2001 From: schneems Date: Sun, 19 Jul 2015 16:19:15 -0500 Subject: Freeze string literals when not mutated. MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit I wrote a utility that helps find areas where you could optimize your program using a frozen string instead of a string literal, it's called [let_it_go](https://github.com/schneems/let_it_go). After going through the output and adding `.freeze` I was able to eliminate the creation of 1,114 string objects on EVERY request to [codetriage](codetriage.com). How does this impact execution? To look at memory: ```ruby require 'get_process_mem' mem = GetProcessMem.new GC.start GC.disable 1_114.times { " " } before = mem.mb after = mem.mb GC.enable puts "Diff: #{after - before} mb" ``` Creating 1,114 string objects results in `Diff: 0.03125 mb` of RAM allocated on every request. Or 1mb every 32 requests. To look at raw speed: ```ruby require 'benchmark/ips' number_of_objects_reduced = 1_114 Benchmark.ips do |x| x.report("freeze") { number_of_objects_reduced.times { " ".freeze } } x.report("no-freeze") { number_of_objects_reduced.times { " " } } end ``` We get the results ``` Calculating ------------------------------------- freeze 1.428k i/100ms no-freeze 609.000 i/100ms ------------------------------------------------- freeze 14.363k (± 8.5%) i/s - 71.400k no-freeze 6.084k (± 8.1%) i/s - 30.450k ``` Now we can do some maths: ```ruby ips = 6_226k # iterations / 1 second call_time_before = 1.0 / ips # seconds per iteration ips = 15_254 # iterations / 1 second call_time_after = 1.0 / ips # seconds per iteration diff = call_time_before - call_time_after number_of_objects_reduced * diff * 100 # => 0.4530373333993266 miliseconds saved per request ``` So we're shaving off 1 second of execution time for every 220 requests. Is this going to be an insane speed boost to any Rails app: nope. Should we merge it: yep. p.s. If you know of a method call that doesn't modify a string input such as [String#gsub](https://github.com/schneems/let_it_go/blob/b0e2da69f0cca87ab581022baa43291cdf48638c/lib/let_it_go/core_ext/string.rb#L37) please [give me a pull request to the appropriate file](https://github.com/schneems/let_it_go/blob/b0e2da69f0cca87ab581022baa43291cdf48638c/lib/let_it_go/core_ext/string.rb#L37), or open an issue in LetItGo so we can track and freeze more strings. Keep those strings Frozen ![](https://www.dropbox.com/s/z4dj9fdsv213r4v/let-it-go.gif?dl=1) --- activesupport/lib/active_support/message_verifier.rb | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) (limited to 'activesupport/lib/active_support/message_verifier.rb') diff --git a/activesupport/lib/active_support/message_verifier.rb b/activesupport/lib/active_support/message_verifier.rb index b2a4404968..64c5232cf4 100644 --- a/activesupport/lib/active_support/message_verifier.rb +++ b/activesupport/lib/active_support/message_verifier.rb @@ -46,7 +46,7 @@ module ActiveSupport def valid_message?(signed_message) return if signed_message.nil? || !signed_message.valid_encoding? || signed_message.blank? - data, digest = signed_message.split("--") + data, digest = signed_message.split("--".freeze) data.present? && digest.present? && ActiveSupport::SecurityUtils.secure_compare(digest, generate_digest(data)) end @@ -74,7 +74,7 @@ module ActiveSupport def verified(signed_message) if valid_message?(signed_message) begin - data = signed_message.split("--")[0] + data = signed_message.split("--".freeze)[0] @serializer.load(decode(data)) rescue ArgumentError => argument_error return if argument_error.message =~ %r{invalid base64} -- cgit v1.2.3