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diff --git a/doc/development/profiling.md b/doc/development/profiling.md index deb743569c5..a3142b06e12 100644 --- a/doc/development/profiling.md +++ b/doc/development/profiling.md @@ -91,6 +91,73 @@ printer = RubyProf::CallStackPrinter.new(result) printer.print(File.open('/tmp/profile.html', 'w')) ``` +### Stackprof support + +By default, `Gitlab::Profiler.profile` uses a tracing profiler called [`ruby-prof`](https://ruby-prof.github.io/). However, sampling profilers +[run faster and use less memory](https://jvns.ca/blog/2017/12/17/how-do-ruby---python-profilers-work-/), so they might be preferred. + +You can switch to [Stackprof](https://github.com/tmm1/stackprof) (a sampling profiler) to generate a profile by passing `sampling_mode: true`. +Pass in a `profiler_options` hash to configure the output file (`out`) of the sampling data. For example: + +```ruby +Gitlab::Profiler.profile('/gitlab-org/gitlab-test', user: User.first, sampling_mode: true, profiler_options: { out: 'tmp/profile.dump' }) +``` + +You can get a summary of where time was spent by running Stackprof against the sampling data. For example: + +```shell +stackprof tmp/profile.dump +``` + +Example sampling data: + +```plaintext +================================== + Mode: wall(1000) + Samples: 8745 (6.92% miss rate) + GC: 1399 (16.00%) +================================== + TOTAL (pct) SAMPLES (pct) FRAME + 1022 (11.7%) 1022 (11.7%) Sprockets::PathUtils#stat + 957 (10.9%) 957 (10.9%) (marking) + 493 (5.6%) 493 (5.6%) Sprockets::PathUtils#entries + 576 (6.6%) 471 (5.4%) Mustermann::AST::Translator#decorator_for + 439 (5.0%) 439 (5.0%) (sweeping) + 630 (7.2%) 241 (2.8%) Sprockets::Cache::FileStore#get + 208 (2.4%) 208 (2.4%) ActiveSupport::FileUpdateChecker#watched + 206 (2.4%) 206 (2.4%) Digest::Instance#file + 544 (6.2%) 176 (2.0%) Sprockets::Cache::FileStore#safe_open + 176 (2.0%) 176 (2.0%) ActiveSupport::FileUpdateChecker#max_mtime + 268 (3.1%) 147 (1.7%) ActiveRecord::ConnectionAdapters::PostgreSQLAdapter#exec_no_cache + 140 (1.6%) 140 (1.6%) ActiveSupport::BacktraceCleaner#add_gem_filter + 116 (1.3%) 116 (1.3%) Bootsnap::CompileCache::ISeq.storage_to_output + 160 (1.8%) 113 (1.3%) Gem::Version#<=> + 109 (1.2%) 109 (1.2%) block in <main> + 108 (1.2%) 108 (1.2%) Gem::Version.new + 131 (1.5%) 105 (1.2%) Sprockets::EncodingUtils#unmarshaled_deflated + 1166 (13.3%) 82 (0.9%) Mustermann::RegexpBased#initialize + 82 (0.9%) 78 (0.9%) FileUtils.touch + 72 (0.8%) 72 (0.8%) Sprockets::Manifest.compile_match_filter + 71 (0.8%) 70 (0.8%) Grape::Router#compile! + 91 (1.0%) 65 (0.7%) ActiveRecord::ConnectionAdapters::PostgreSQL::DatabaseStatements#query + 93 (1.1%) 64 (0.7%) ActionDispatch::Journey::Path::Pattern::AnchoredRegexp#accept + 59 (0.7%) 59 (0.7%) Mustermann::AST::Translator.dispatch_table + 62 (0.7%) 59 (0.7%) Rails::BacktraceCleaner#initialize + 2492 (28.5%) 49 (0.6%) Sprockets::PathUtils#stat_directory + 242 (2.8%) 49 (0.6%) Gitlab::Instrumentation::RedisBase.add_call_details + 47 (0.5%) 47 (0.5%) URI::RFC2396_Parser#escape + 46 (0.5%) 46 (0.5%) #<Class:0x00000001090c2e70>#__setobj__ + 44 (0.5%) 44 (0.5%) Sprockets::Base#normalize_logical_path +``` + +You can also generate flamegraphs: + +```shell +stackprof --d3-flamegraph tmp/profile.dump > flamegraph.html +``` + +See [the Stackprof documentation](https://github.com/tmm1/stackprof) for more details. + ## Speedscope flamegraphs You can generate a flamegraph for a particular URL by selecting a flamegraph sampling mode button in the performance bar or by adding the `performance_bar=flamegraph` parameter to the request. |