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# frozen_string_literal: true
# This class uses a custom Ruby patch to allow
# a per-thread memory allocation tracking in a efficient manner
#
# This concept is currently tried to be upstreamed here:
# - https://github.com/ruby/ruby/pull/3978
module Gitlab
module Memory
class Instrumentation
KEY_MAPPING = {
total_allocated_objects: :mem_objects,
total_malloc_bytes: :mem_bytes,
total_mallocs: :mem_mallocs
}.freeze
MUTEX = Mutex.new
def self.available?
Thread.respond_to?(:trace_memory_allocations=) &&
Thread.current.respond_to?(:memory_allocations)
end
def self.start_thread_memory_allocations
return unless available?
MUTEX.synchronize do
# This method changes a global state
Thread.trace_memory_allocations = true
end
# it will return `nil` if disabled
Thread.current.memory_allocations
end
# This method returns a hash with the following keys:
# - mem_objects: number of allocated heap slots (as reflected by GC)
# - mem_mallocs: number of malloc calls
# - mem_bytes: number of bytes allocated by malloc for objects that did not fit
# into a heap slot
# - mem_total_bytes: number of bytes allocated for both objects consuming an object slot
# and objects that required a malloc (mem_malloc_bytes)
def self.measure_thread_memory_allocations(previous)
return unless available?
return unless previous
current = Thread.current.memory_allocations
return unless current
# calculate difference in a memory allocations
result = previous.to_h do |key, value|
[KEY_MAPPING.fetch(key), current[key].to_i - value]
end
result[:mem_total_bytes] = result[:mem_bytes] + result[:mem_objects] * GC::INTERNAL_CONSTANTS[:RVALUE_SIZE]
result
end
def self.with_memory_allocations
previous = self.start_thread_memory_allocations
yield
self.measure_thread_memory_allocations(previous)
end
end
end
end
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