231 lines
9.1 KiB
Markdown
231 lines
9.1 KiB
Markdown
---
|
|
stage: none
|
|
group: unassigned
|
|
info: To determine the technical writer assigned to the Stage/Group associated with this page, see https://about.gitlab.com/handbook/engineering/ux/technical-writing/#assignments
|
|
---
|
|
|
|
# Profiling
|
|
|
|
To make it easier to track down performance problems GitLab comes with a set of
|
|
profiling tools, some of these are available by default while others need to be
|
|
explicitly enabled.
|
|
|
|
## Profiling a URL
|
|
|
|
There is a `Gitlab::Profiler.profile` method, and corresponding
|
|
`bin/profile-url` script, that enable profiling a GET or POST request to a
|
|
specific URL, either as an anonymous user (the default) or as a specific user.
|
|
|
|
The first argument to the profiler is either a full URL
|
|
(including the instance hostname) or an absolute path, including the
|
|
leading slash.
|
|
|
|
When using the script, command-line documentation is available by passing no
|
|
arguments.
|
|
|
|
When using the method in an interactive console session, any changes to the
|
|
application code within that console session is reflected in the profiler
|
|
output.
|
|
|
|
For example:
|
|
|
|
```ruby
|
|
Gitlab::Profiler.profile('/my-user')
|
|
# Returns a RubyProf::Profile for the regular operation of this request
|
|
class UsersController; def show; sleep 100; end; end
|
|
Gitlab::Profiler.profile('/my-user')
|
|
# Returns a RubyProf::Profile where 100 seconds is spent in UsersController#show
|
|
```
|
|
|
|
For routes that require authorization you must provide a user to
|
|
`Gitlab::Profiler`. You can do this like so:
|
|
|
|
```ruby
|
|
Gitlab::Profiler.profile('/gitlab-org/gitlab-test', user: User.first)
|
|
```
|
|
|
|
Passing a `logger:` keyword argument to `Gitlab::Profiler.profile` sends
|
|
ActiveRecord and ActionController log output to that logger. Further options are
|
|
documented with the method source.
|
|
|
|
```ruby
|
|
Gitlab::Profiler.profile('/gitlab-org/gitlab-test', user: User.first, logger: Logger.new($stdout))
|
|
```
|
|
|
|
There is also a RubyProf printer available:
|
|
`Gitlab::Profiler::TotalTimeFlatPrinter`. This acts like
|
|
`RubyProf::FlatPrinter`, but its `min_percent` option works on the method's
|
|
total time, not its self time. (This is because we often spend most of our time
|
|
in library code, but this comes from calls in our application.) It also offers a
|
|
`max_percent` option to help filter out outer calls that aren't useful (like
|
|
`ActionDispatch::Integration::Session#process`).
|
|
|
|
There is a convenience method for using this,
|
|
`Gitlab::Profiler.print_by_total_time`:
|
|
|
|
```ruby
|
|
result = Gitlab::Profiler.profile('/my-user')
|
|
Gitlab::Profiler.print_by_total_time(result, max_percent: 60, min_percent: 2)
|
|
# Measure Mode: wall_time
|
|
# Thread ID: 70005223698240
|
|
# Fiber ID: 70004894952580
|
|
# Total: 1.768912
|
|
# Sort by: total_time
|
|
#
|
|
# %self total self wait child calls name
|
|
# 0.00 1.017 0.000 0.000 1.017 14 *ActionView::Helpers::RenderingHelper#render
|
|
# 0.00 1.017 0.000 0.000 1.017 14 *ActionView::Renderer#render_partial
|
|
# 0.00 1.017 0.000 0.000 1.017 14 *ActionView::PartialRenderer#render
|
|
# 0.00 1.007 0.000 0.000 1.007 14 *ActionView::PartialRenderer#render_partial
|
|
# 0.00 0.930 0.000 0.000 0.930 14 Hamlit::TemplateHandler#call
|
|
# 0.00 0.928 0.000 0.000 0.928 14 Temple::Engine#call
|
|
# 0.02 0.865 0.000 0.000 0.864 638 *Enumerable#inject
|
|
```
|
|
|
|
To print the profile in HTML format, use the following example:
|
|
|
|
```ruby
|
|
result = Gitlab::Profiler.profile('/my-user')
|
|
|
|
printer = RubyProf::CallStackPrinter.new(result)
|
|
printer.print(File.open('/tmp/profile.html', 'w'))
|
|
```
|
|
|
|
[GitLab-Profiler](https://gitlab.com/gitlab-com/gitlab-profiler) is a project
|
|
that builds on this to add some additional niceties, such as allowing
|
|
configuration with a single YAML file for multiple URLs, and uploading of the
|
|
profile and log output to S3.
|
|
|
|
## 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.
|
|
|
|
|
|
|
|
Find more information about the views in the [Speedscope docs](https://github.com/jlfwong/speedscope#views).
|
|
|
|
Find more information about different sampling modes in the [Stackprof docs](https://github.com/tmm1/stackprof#sampling).
|
|
|
|
This is enabled for all users that can access the performance bar.
|
|
|
|
## Bullet
|
|
|
|
Bullet is a Gem that can be used to track down N+1 query problems. Bullet section is
|
|
displayed on the [performance-bar](../administration/monitoring/performance/performance_bar.md).
|
|
|
|
|
|
|
|
Because Bullet adds quite a bit of logging noise the logging is disabled by default.
|
|
To enable the logging, set the environment variable `ENABLE_BULLET` to a non-empty value before
|
|
starting GitLab. For example:
|
|
|
|
```shell
|
|
ENABLE_BULLET=true bundle exec rails s
|
|
```
|
|
|
|
Bullet logs query problems to both the Rails log as well as the browser
|
|
console.
|
|
|
|
As a follow up to finding `N+1` queries with Bullet, consider writing a [QueryRecoder test](query_recorder.md) to prevent a regression.
|
|
|
|
## System stats
|
|
|
|
During or after profiling, you may want to get detailed information about the Ruby virtual machine process,
|
|
such as memory consumption, time spent on CPU, or garbage collector statistics. These are easy to produce individually
|
|
through various tools, but for convenience, a summary endpoint has been added that exports this data as a JSON payload:
|
|
|
|
```shell
|
|
curl localhost:3000/-/metrics/system | jq
|
|
```
|
|
|
|
Example output:
|
|
|
|
```json
|
|
{
|
|
"version": "ruby 2.7.2p137 (2020-10-01 revision a8323b79eb) [x86_64-linux-gnu]",
|
|
"gc_stat": {
|
|
"count": 118,
|
|
"heap_allocated_pages": 11503,
|
|
"heap_sorted_length": 11503,
|
|
"heap_allocatable_pages": 0,
|
|
"heap_available_slots": 4688580,
|
|
"heap_live_slots": 3451712,
|
|
"heap_free_slots": 1236868,
|
|
"heap_final_slots": 0,
|
|
"heap_marked_slots": 3451450,
|
|
"heap_eden_pages": 11503,
|
|
"heap_tomb_pages": 0,
|
|
"total_allocated_pages": 11503,
|
|
"total_freed_pages": 0,
|
|
"total_allocated_objects": 32679478,
|
|
"total_freed_objects": 29227766,
|
|
"malloc_increase_bytes": 84760,
|
|
"malloc_increase_bytes_limit": 32883343,
|
|
"minor_gc_count": 88,
|
|
"major_gc_count": 30,
|
|
"compact_count": 0,
|
|
"remembered_wb_unprotected_objects": 114228,
|
|
"remembered_wb_unprotected_objects_limit": 228456,
|
|
"old_objects": 3185330,
|
|
"old_objects_limit": 6370660,
|
|
"oldmalloc_increase_bytes": 21838024,
|
|
"oldmalloc_increase_bytes_limit": 119181499
|
|
},
|
|
"memory_rss": 1326501888,
|
|
"memory_uss": 1048563712,
|
|
"memory_pss": 1139554304,
|
|
"time_cputime": 82.885264633,
|
|
"time_realtime": 1610459445.5579069,
|
|
"time_monotonic": 24001.23145713,
|
|
"worker_id": "puma_0"
|
|
}
|
|
```
|
|
|
|
NOTE:
|
|
This endpoint is only available for Rails web workers. Sidekiq workers can not be inspected this way.
|
|
|
|
## Settings that impact performance
|
|
|
|
### Application settings
|
|
|
|
1. `development` environment by default works with hot-reloading enabled, this makes Rails to check file changes every request, and create a potential contention lock, as hot reload is single threaded.
|
|
1. `development` environment can load code lazily once the request is fired which results in first request to always be slow.
|
|
|
|
To disable those features for profiling/benchmarking set the `RAILS_PROFILE` environment variable to `true` before starting GitLab. For example when using GDK:
|
|
|
|
- create a file [`env.runit`](https://gitlab.com/gitlab-org/gitlab-development-kit/-/blob/main/doc/runit.md#modifying-environment-configuration-for-services) in the root GDK directory
|
|
- add `export RAILS_PROFILE=true` to your `env.runit` file
|
|
- restart GDK with `gdk restart`
|
|
|
|
*This environment variable is only applicable for the development mode.*
|
|
|
|
### GC settings
|
|
|
|
Ruby's garbage collector (GC) can be tuned via a variety of environment variables that will directly impact application performance.
|
|
|
|
The following table lists these variables along with their default values.
|
|
|
|
| Environment variable | Default value |
|
|
|--|--|
|
|
| `RUBY_GC_HEAP_INIT_SLOTS` | `10000` |
|
|
| `RUBY_GC_HEAP_FREE_SLOTS` | `4096` |
|
|
| `RUBY_GC_HEAP_FREE_SLOTS_MIN_RATIO` | `0.20` |
|
|
| `RUBY_GC_HEAP_FREE_SLOTS_GOAL_RATIO` | `0.40` |
|
|
| `RUBY_GC_HEAP_FREE_SLOTS_MAX_RATIO` | `0.65` |
|
|
| `RUBY_GC_HEAP_GROWTH_FACTOR` | `1.8` |
|
|
| `RUBY_GC_HEAP_GROWTH_MAX_SLOTS` | `0 (disable)` |
|
|
| `RUBY_GC_HEAP_OLDOBJECT_LIMIT_FACTOR` | `2.0` |
|
|
| `RUBY_GC_MALLOC_LIMIT(_MIN)` | `(16 * 1024 * 1024 /* 16MB */)` |
|
|
| `RUBY_GC_MALLOC_LIMIT_MAX` | `(32 * 1024 * 1024 /* 32MB */)` |
|
|
| `RUBY_GC_MALLOC_LIMIT_GROWTH_FACTOR` | `1.4` |
|
|
| `RUBY_GC_OLDMALLOC_LIMIT(_MIN)` | `(16 * 1024 * 1024 /* 16MB */)` |
|
|
| `RUBY_GC_OLDMALLOC_LIMIT_MAX` | `(128 * 1024 * 1024 /* 128MB */)` |
|
|
| `RUBY_GC_OLDMALLOC_LIMIT_GROWTH_FACTOR` | `1.2` |
|
|
|
|
([Source](https://github.com/ruby/ruby/blob/45b29754cfba8435bc4980a87cd0d32c648f8a2e/gc.c#L254-L308))
|
|
|
|
GitLab may decide to change these settings in order to speed up application performance, lower memory requirements, or both.
|
|
|
|
You can see how each of these settings affect GC performance, memory use and application start-up time for an idle instance of
|
|
GitLab by running the `scripts/perf/gc/collect_gc_stats.rb` script. It will output GC stats and general timing data to standard
|
|
out as CSV.
|