Profile a Protected Audience auction

Protected Audience auctions can be analyzed (either visually or by SQL query with Perfetto. Ad techs can use profiling with Perfetto to measure the performance of Protected Audience auctions, including:

Bidding and scoring script CPU time
Latency of HTTP requests such as key/value service
Performance impact of cold cache versus hot cache
More versus fewer custom audiences
Larger versus smaller sets of signals
Different bidding logic scripts per custom audience as compared to using the same script for all bidding

Setup

Clone the Perfetto and Privacy Sandbox repositories.

git clone https://android.googlesource.com/platform/external/perfetto
git clone https://github.com/android/privacy-sandbox-samples

In Android Studio, open the Protected Audience sample app from the privacy-sandbox-samples/Fledge/FledgeKotlin directory.
Build and install the sample app on your test device or emulator.

Run an auction and take a Perfetto trace

Set up and deploy test HTTPS endpoints. Take a note of the URL of the hosted endpoints as they're required for the Protected Audience demo app to function.
Launch the demo app with a test endpoint URL specified. Replace <test-endpoint-url> with a hosted endpoint URL that you recorded in the previous step.
```
adb shell am start -n com.example.adservices.samples.fledge.sampleapp/.MainActivity \
  -e baseUrl "<test-endpoint-url>"
```
Toggle the "Shoes CA" to ensure there's at least 1 custom audience active.

Protected Audience Demo App.
Record a trace using the trace_config.textproto file from the Privacy Sandbox DevTools GitHub repository:
```
./perfetto/tools/record_android_trace \
  -c path/to/trace_config.textproto
```
Tap the "Run Ad Selection" button and wait for the auction results. When the auction completes, the output displays a message such as "Would display ad from http://example.com/bidding/render_shoes".
In your terminal, terminate (CTRL+C) the record_android_trace program to finish the trace. The Perfetto UI opens in your browser with the trace data loaded.

Visually explore traces in Perfetto

Search for "RunOnDeviceAdSelection" using the address bar at the top of the UI. Click Enter to complete the search and show the results:

Single-buyer Protected Audience auction in Perfetto.
Click a trace to inspect it. Details such as execution latency are available here.

Inspecting a trace segment.

Protected Audience-specific trace segments

The Protected Audience auction is a complex process and there are many different segments captured by the Perfetto trace. This table documents what each trace segment represents.

Time	Segment	Description	Frequency
Pre auction	`RunOnDeviceAdSelection`	Auction end-to-end	Per auction
Bidding (buy-side)	`FilterContextualAds`	Perform app install and frequency cap filtering on contextual ads	Per auction
	`GetBuyersCustomAudience`	Load buyer's custom audience from database	Per buyer
	`FilterCustomAudiences`	Perform app install and frequency cap filtering on custom audiences	Per auction
	`GetTrustedBiddingSignals`	Load buyer's bidding signals	Per buyer
	`RunBiddingPerCustomAudience`	Ad bidding for a single custom audience	Per custom audience
	`GetBuyerDecisionLogic`	Load buyer's JavaScript from the network, or database, if cached	Per custom audience
	`RunBidding`	JavaScript execution for a buyer	Per buyer
	`GenerateBids`	JavaScript execution for a custom audience	Per custom audience
Scoring (sell-side)	`GetTrustedScoringSignals`	Load seller's scoring signals	Per seller
	`RunAdScoring`	JavaScript execution for scoring	Per auction
	`ScoreAd`	JavaScript execution for an ad	Per ad
	`GetAdSelectionLogic`	Load seller's ad selection logic	Per auction
	`RunAdOutcomeSelection`	Final filtering	Per auction
Post auction	`PersistOnDeviceAdSelection`	Write auction result to database	Per auction

Query for average execution latency

Perfetto can use SQL queries to get precise measurement of what's happening inside a particular trace.

This section documents how to measure the average execution latency for JavaScript execution.

In Perfetto, navigate to "Query (SQL)" in the left navigation pane.

Enter the following query:

SELECT AVG(dur)
FROM slice
WHERE slice.name GLOB 'FetchPayload';

Run the query and inspect the results.

SQL query results in nanoseconds.