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Reduce memory usage during gem statup #1090

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merged 4 commits into from Sep 21, 2020
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@marcotc marcotc commented Jun 18, 2020

This PR introduces a few changes guide by the results from our new startup benchmarks: #1062.

The largest memory footprint we have as a gem is loading external dependencies (through require) and loading our own Ruby files.

Most of our dependencies will likely be used by the host application (e.g. thread, logger, sockets), so their overhead is shared with the host.

A few "unique" dependencies showed up, like msgpack, but they are required for the correct function of the tracer.

Another PR will follow with changes to load integration code dynamically, which should have the largest impact, based on my local testing.

This PR is an aggregation of a few changes that showed up as relevant enough in the benchmarks and that don't require large rework, nor introduce large risks.

This PR should have the following performance impact:

  • Retained memory:
    • Retained objects: 7,116 -> 7,030 (2% reduction)
    • Retained memory: 899,078 -> 895,471 (0.5% reduction)
  • Startup time: 137 ms -> 133 ms (3% reduction)
  • Total RubyVM RSS memory: 7320 KiB (no change)

@marcotc marcotc added core Involves Datadog core libraries performance Involves performance (e.g. CPU, memory, etc) labels Jun 18, 2020
@marcotc marcotc requested a review from a team June 18, 2020 19:49
@marcotc marcotc self-assigned this Jun 18, 2020
@@ -26,7 +26,8 @@ def option(name, meta = {}, &block)
builder = OptionDefinition::Builder.new(name, meta, &block)
options[name] = builder.to_definition.tap do
# Resolve and define helper functions
helpers = default_helpers(name).merge(builder.helpers)
helpers = default_helpers(name)
helpers = helpers.merge(builder.helpers) unless builder.helpers.empty?
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Merging with an empty hash creates an unnecessary copy of the original hash.

o.default false
o.on_set do |enabled|
# Enable rich debug print statements
require 'pp' if enabled
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@marcotc marcotc Jun 18, 2020

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Loading of pp is now lazy, as it is only used in production ddtrace when debug diagnostics are enabled.

Although pp is commonly used in testing and development, the host application is not guaranteed to need it in production mode.

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nice work! My only feedback would be, maybe we don't need pretty print at all? probably not worth the change if it accidentally breaks some log parsing somewhere

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@marcotc None of these test failures seem related afaik

@marcotc marcotc merged commit 1ac9142 into master Sep 21, 2020
@marcotc marcotc deleted the feat/less-memory-startup branch September 21, 2020 19:14
@ericmustin ericmustin added this to the 0.41.0 milestone Sep 30, 2020
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