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# frozen_string_literal: true
require 'fiddle'
module Gitlab
module Memory
module Jemalloc
extend self
STATS_FORMATS = {
json: { options: 'J', extension: 'json' },
text: { options: '', extension: 'txt' }
}.freeze
STATS_DEFAULT_FORMAT = :json
FILENAME_PREFIX = 'jemalloc_stats'
# Return jemalloc stats as a string.
def stats(format: STATS_DEFAULT_FORMAT)
verify_format!(format)
with_malloc_stats_print do |stats_print|
StringIO.new.tap { |io| write_stats(stats_print, io, STATS_FORMATS[format]) }.string
end
end
# Write jemalloc stats to the given directory
# @param [String] path Directory path the dump will be put into
# @param [String] format `json` or `txt`
# @param [String] filename_label Optional custom string that will be injected into the file name, e.g. `worker_0`
# @return [String] Full path to the resulting dump file
def dump_stats(path:, format: STATS_DEFAULT_FORMAT, filename_label: nil)
verify_format!(format)
format_settings = STATS_FORMATS[format]
file_path = File.join(path, file_name(format_settings[:extension], filename_label))
with_malloc_stats_print do |stats_print|
File.open(file_path, 'wb') do |io|
write_stats(stats_print, io, format_settings)
end
end
file_path
end
private
def verify_format!(format)
raise "format must be one of #{STATS_FORMATS.keys}" unless STATS_FORMATS.key?(format)
end
def with_malloc_stats_print
fiddle_func = malloc_stats_print
return unless fiddle_func
yield fiddle_func
end
def malloc_stats_print
method = Fiddle::Handle.sym("malloc_stats_print")
Fiddle::Function.new(
method,
# C signature:
# void (write_cb_t *write_cb, void *cbopaque, const char *opts)
# arg1: callback function pointer (see below)
# arg2: pointer to cbopaque holding additional callback data; always NULL here
# arg3: options string, affects output format (text or JSON)
#
# Callback signature (write_cb_t):
# void (void *, const char *)
# arg1: pointer to cbopaque data (see above; unused)
# arg2: pointer to string buffer holding textual output
[Fiddle::TYPE_VOIDP, Fiddle::TYPE_VOIDP, Fiddle::TYPE_VOIDP],
Fiddle::TYPE_VOID
)
rescue Fiddle::DLError
# This means the Fiddle::Handle to jemalloc was not open (jemalloc wasn't loaded)
# or already closed. Eiher way, return nil.
end
def write_stats(stats_print, io, format)
callback = Fiddle::Closure::BlockCaller.new(
Fiddle::TYPE_VOID, [Fiddle::TYPE_VOIDP, Fiddle::TYPE_VOIDP]) do |_, fragment|
io << fragment
end
stats_print.call(callback, nil, format[:options])
end
def file_name(extension, filename_label)
[FILENAME_PREFIX, $$, filename_label, Time.current.to_i, extension].reject(&:blank?).join('.')
end
end
end
end
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