gh-140677 Add heatmap visualization to Tachyon sampling profiler#140680

pablogsal · 2025-10-27T17:01:25Z

Introduce a new --heatmap output format that provides line-by-line
execution visualization. The heatmap shows:

Color-coded execution intensity for each line (cold → warm → hot → very hot)
Inline sample counts and percentages per line
Per-file statistics (total samples, hottest line)
Interactive call graph navigation with caller/callee buttons
Module type badges (stdlib, site-packages, project code)

Unlike flamegraphs which show call stacks and time distribution, heatmaps
excel at identifying hot code paths within files, understanding line-level
execution patterns, and navigating through call relationships.

Issue: Add a new heatmap output to the tachyon profiler #140677

pablogsal · 2025-10-27T17:05:39Z

CC @ambv

Introduce a new --heatmap output format that provides line-by-line execution visualization. The heatmap shows: - Color-coded execution intensity for each line (cold → warm → hot → very hot) - Inline sample counts and percentages per line - Per-file statistics (total samples, hottest line) - Interactive call graph navigation with caller/callee buttons - Module type badges (stdlib, site-packages, project code) Unlike flamegraphs which show call stacks and time distribution, heatmaps excel at identifying hot code paths within files, understanding line-level execution patterns, and navigating through call relationships.

savannahostrowski

Okay, this is so cool! I left a couple of comments, but also wanted to mention that I really loved that you added a minimap to show hotspots and the permalinking on line click; so nice for jumping around and sharing results.

Lib/profiling/sampling/heatmap_index_template.html

Lib/profiling/sampling/stack_collector.py

Lib/profiling/sampling/sample.py

pablogsal · 2025-11-24T20:24:21Z

CC @ivonastojanovic can you give this a pass when you have some time? Test it locally and play a bit with it before reviewing the code

pablogsal · 2025-11-30T02:30:39Z

@ivonastojanovic I have updated the buttons to be toggles, pls take a look

ivonastojanovic

This looks great! I left a few comments, and I’ll experiment with the CSS a bit

ivonastojanovic · 2025-12-01T21:01:26Z

Lib/profiling/sampling/heatmap_collector.py

+ tree = trees[module_type]
+
+ # Project starts expanded, others start collapsed
+ is_collapsed = module_type in ('stdlib', 'site-packages')


Should the other files be collapsed by default? Since this category typically includes special frames or uncategorized files, users are usually more interested in their own project code first. Collapsing these by default might make navigation clearer?

Lib/profiling/sampling/heatmap_collector.py

Small changes: - Change navigation button colors for dark theme - Update toggle button colors and active-state text - Add missing "→" in the Intensity legend

ivonastojanovic · 2025-12-02T00:21:46Z

@pablogsal I ran into a bug during testing, so with Total and Hot enabled, changing the theme makes the sidebar vanish 👀

Screen.Recording.2025-12-02.at.00.15.56.mov

Co-authored-by: ivonastojanovic <[email protected]>

pablogsal · 2025-12-02T15:05:48Z

@pablogsal I ran into a bug during testing, so with Total and Hot enabled, changing the theme makes the sidebar vanish 👀
Screen.Recording.2025-12-02.at.00.15.56.mov

Good catch! Fixed :)

ivonastojanovic

LGTM 🚀

pablogsal · 2025-12-02T20:33:52Z

Thanks a lot @ivonastojanovic and @savannahostrowski for the reviews!

python#140680) Co-authored-by: Ivona Stojanovic <[email protected]>

bedevere-appbot mentioned this pull request Oct 27, 2025
Add a new heatmap output to the tachyon profiler #140677
Closed

pablogsal force-pushed the heatmap branch 2 times, most recently from b1d5307 to 9ee2b80Compare October 27, 2025 17:04

pablogsal requested a review from ambv October 27, 2025 17:05

pablogsal force-pushed the heatmap branch from 9ee2b80 to 51c3f34Compare October 27, 2025 17:08

savannahostrowski reviewed Oct 28, 2025
View reviewed changes

pablogsal added 2 commits October 29, 2025 14:13

fixup! Add heatmap visualization to Tachyon sampling profiler
02a379d

Add scroll to caller/callee menu
e1ef737

pablogsal changed the title ~~gh-140677 :Add heatmap visualization to Tachyon sampling profiler~~gh-140677 Add heatmap visualization to Tachyon sampling profilerNov 24, 2025

Merge upstream/main into heatmap branch
fd62937

pablogsal force-pushed the heatmap branch from 18b50aa to fd62937Compare November 24, 2025 12:32

pablogsal added 4 commits November 24, 2025 12:32

fixup! Merge upstream/main into heatmap branch
00cd05e

UX improvements
4fa26c0

Imrpovements
ece3617

MOAR refactor
aa08ce0

pablogsal marked this pull request as ready for review November 24, 2025 14:11

bedevere-appbot added the awaiting core review label Nov 24, 2025

pablogsal added 2 commits November 24, 2025 19:42

fixup! MOAR refactor
09b132d

fixup! fixup! MOAR refactor
9a42111

pablogsal requested review from AA-Turner, emmatyping and erlend-aasland as code owners November 24, 2025 20:23

pablogsal requested a review from ivonastojanovic November 24, 2025 20:23

pablogsal added 2 commits November 30, 2025 02:19

Merge remote-tracking branch 'upstream/main' into heatmap
cca0057

use toggles
d726488

Respect the self-time toggle in hot only
b695f7a

pablogsal added 5 commits December 1, 2025 17:36

Merge remote-tracking branch 'upstream/main' into heatmap
87037d8

pythongh-138122: Small fixes to the new tachyon UI
87838a7

Merge remote-tracking branch 'upstream/main' into heatmap
27187d8

Restyle heatmap like flamegraph
07835e9

Refactor css into common files
85b5f29

ivonastojanovic reviewed Dec 1, 2025
View reviewed changes

Update UI colors and fix intensity legend
2f9f433
Small changes: - Change navigation button colors for dark theme - Update toggle button colors and active-state text - Add missing "→" in the Intensity legend

pablogsaland others added 2 commits December 2, 2025 14:34

Fix minimap with hot only toggle
42bc9a9

Update Lib/profiling/sampling/heatmap_collector.py
0ca6850
Co-authored-by: ivonastojanovic <[email protected]>

pablogsal added 2 commits December 2, 2025 15:38

Update makefile
446f762

Collapse 'other'
8b78959

ivonastojanovic approved these changes Dec 2, 2025
View reviewed changes

pablogsal merged commit 8801c6d into python:mainDec 2, 2025
46 checks passed

pablogsal deleted the heatmap branch December 2, 2025 20:33

bedevere-appbot removed the awaiting core review label Dec 2, 2025

StanFromIreland pushed a commit to StanFromIreland/cpython that referenced this pull request Dec 6, 2025
pythongh-140677Add heatmap visualization to Tachyon sampling profiler (
b8bc19c
python#140680) Co-authored-by: Ivona Stojanovic <[email protected]>

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gh-140677 Add heatmap visualization to Tachyon sampling profiler #140680

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