From e31dc15d5a2c8eaa3720ffe1cac29eb9f6083a7c Mon Sep 17 00:00:00 2001
From: Neel Shah <neel.shah@sentry.io>
Date: Fri, 27 Mar 2026 16:33:30 +0100
Subject: [PATCH] perf: Use FilenameCache in profilers

---
 .../sentry/interfaces/stacktrace_builder.rb   |  3 +++
 sentry-ruby/lib/sentry/profiler.rb            |  1 +
 sentry-ruby/lib/sentry/profiler/helpers.rb    | 22 +------------------
 .../lib/sentry/utils/filename_cache.rb        |  2 ++
 sentry-ruby/lib/sentry/vernier/output.rb      |  3 ++-
 sentry-ruby/lib/sentry/vernier/profiler.rb    |  4 +++-
 sentry-ruby/spec/sentry/profiler_spec.rb      | 16 ++++++++++++++
 7 files changed, 28 insertions(+), 23 deletions(-)

diff --git a/sentry-ruby/lib/sentry/interfaces/stacktrace_builder.rb b/sentry-ruby/lib/sentry/interfaces/stacktrace_builder.rb
index 14bea700b..c7595cf39 100644
--- a/sentry-ruby/lib/sentry/interfaces/stacktrace_builder.rb
+++ b/sentry-ruby/lib/sentry/interfaces/stacktrace_builder.rb
@@ -22,6 +22,9 @@ class StacktraceBuilder
     # @return [Boolean]
     attr_reader :strip_backtrace_load_path
 
+    # @return [FilenameCache]
+    attr_reader :filename_cache
+
     # @param project_root [String]
     # @param app_dirs_pattern [Regexp, nil]
     # @param linecache [LineCache]
diff --git a/sentry-ruby/lib/sentry/profiler.rb b/sentry-ruby/lib/sentry/profiler.rb
index ba5b5d525..9e329cdd1 100644
--- a/sentry-ruby/lib/sentry/profiler.rb
+++ b/sentry-ruby/lib/sentry/profiler.rb
@@ -26,6 +26,7 @@ def initialize(configuration)
       @project_root = configuration.project_root
       @app_dirs_pattern = configuration.app_dirs_pattern
       @in_app_pattern = Regexp.new("^(#{@project_root}/)?#{@app_dirs_pattern}")
+      @filename_cache = configuration.stacktrace_builder.filename_cache
     end
 
     def start
diff --git a/sentry-ruby/lib/sentry/profiler/helpers.rb b/sentry-ruby/lib/sentry/profiler/helpers.rb
index 3c446fba0..eaa3167e9 100644
--- a/sentry-ruby/lib/sentry/profiler/helpers.rb
+++ b/sentry-ruby/lib/sentry/profiler/helpers.rb
@@ -9,28 +9,8 @@ def in_app?(abs_path)
         abs_path.match?(@in_app_pattern)
       end
 
-      # copied from stacktrace.rb since I don't want to touch existing code
-      # TODO-neel-profiler try to fetch this from stackprof once we patch
-      # the native extension
       def compute_filename(abs_path, in_app)
-        return nil if abs_path.nil?
-
-        under_project_root = @project_root && abs_path.start_with?(@project_root)
-
-        prefix =
-          if under_project_root && in_app
-            @project_root
-          else
-            longest_load_path = $LOAD_PATH.select { |path| abs_path.start_with?(path.to_s) }.max_by(&:size)
-
-            if under_project_root
-              longest_load_path || @project_root
-            else
-              longest_load_path
-            end
-          end
-
-        prefix ? abs_path[prefix.to_s.chomp(File::SEPARATOR).length + 1..-1] : abs_path
+        @filename_cache.compute_filename(abs_path, in_app, true)
       end
 
       def split_module(name)
diff --git a/sentry-ruby/lib/sentry/utils/filename_cache.rb b/sentry-ruby/lib/sentry/utils/filename_cache.rb
index 0472eaf74..976021d85 100644
--- a/sentry-ruby/lib/sentry/utils/filename_cache.rb
+++ b/sentry-ruby/lib/sentry/utils/filename_cache.rb
@@ -2,6 +2,8 @@
 
 module Sentry
   class FilenameCache
+    attr_reader :cache
+
     def initialize(project_root)
       @project_root = project_root
       @load_paths = $LOAD_PATH.map(&:to_s).sort_by(&:size).reverse.freeze
diff --git a/sentry-ruby/lib/sentry/vernier/output.rb b/sentry-ruby/lib/sentry/vernier/output.rb
index 7002f82a1..10233543f 100644
--- a/sentry-ruby/lib/sentry/vernier/output.rb
+++ b/sentry-ruby/lib/sentry/vernier/output.rb
@@ -10,11 +10,12 @@ class Output
 
       attr_reader :profile
 
-      def initialize(profile, project_root:, in_app_pattern:, app_dirs_pattern:)
+      def initialize(profile, project_root:, in_app_pattern:, app_dirs_pattern:, filename_cache:)
         @profile = profile
         @project_root = project_root
         @in_app_pattern = in_app_pattern
         @app_dirs_pattern = app_dirs_pattern
+        @filename_cache = filename_cache
       end
 
       def to_h
diff --git a/sentry-ruby/lib/sentry/vernier/profiler.rb b/sentry-ruby/lib/sentry/vernier/profiler.rb
index 028f85979..5047119f7 100644
--- a/sentry-ruby/lib/sentry/vernier/profiler.rb
+++ b/sentry-ruby/lib/sentry/vernier/profiler.rb
@@ -24,6 +24,7 @@ def initialize(configuration)
         @project_root = configuration.project_root
         @app_dirs_pattern = configuration.app_dirs_pattern
         @in_app_pattern = Regexp.new("^(#{@project_root}/)?#{@app_dirs_pattern}")
+        @filename_cache = configuration.stacktrace_builder.filename_cache
       end
 
       def set_initial_sample_decision(transaction_sampled)
@@ -125,7 +126,8 @@ def output
           result,
           project_root: @project_root,
           app_dirs_pattern: @app_dirs_pattern,
-          in_app_pattern: @in_app_pattern
+          in_app_pattern: @in_app_pattern,
+          filename_cache: @filename_cache
         )
       end
     end
diff --git a/sentry-ruby/spec/sentry/profiler_spec.rb b/sentry-ruby/spec/sentry/profiler_spec.rb
index 2de41ca13..eea87917e 100644
--- a/sentry-ruby/spec/sentry/profiler_spec.rb
+++ b/sentry-ruby/spec/sentry/profiler_spec.rb
@@ -320,6 +320,22 @@
           last_elapsed = elapsed
         end
       end
+
+      it 'reuses filename_cache entries with stacktrace_builder' do
+        filename_cache = Sentry.configuration.stacktrace_builder.filename_cache
+        spec_path = "#{Dir.pwd}/spec/sentry/profiler_spec.rb"
+
+        # building a stacktrace populates the cache
+        Sentry.configuration.stacktrace_builder.build(
+          backtrace: ["#{spec_path}:7:in `foo'"]
+        )
+
+        expect(filename_cache.cache).to have_key(spec_path)
+
+        # profiler reuses the cached entry instead of recomputing
+        expect(filename_cache).not_to receive(:longest_load_path).with(spec_path)
+        subject.to_h
+      end
     end
   end
 end