Why is yt-dlp built on Python 3.14.0 slower than 3.13.9? Why more bytes read?

[barkoder]

I built yt-dlp --onedir , using both 3.13.9 and 3.14.0 in separate venvs using identical options.

The py3.14.0 yt-dlp.exe consistently performs worse than the py 3.13.9 yt-dlp.exe

$ for i in $(seq 1 10) ; \
do echo -n PY314_ONEDIR- ; \
time C:/yt-dlp314/yt-dlp314.exe --no-config -v 2>&1 | grep real ; \
echo -n PY313_ONEDIR- ; \
time C:/yt-dlp313/yt-dlp313.exe --no-config -v 2>&1 | grep real ; \
echo '----'  ; \
done

PY314_ONEDIR-real       0m 2.28s
PY313_ONEDIR-real       0m 2.06s
----
PY314_ONEDIR-real       0m 2.13s
PY313_ONEDIR-real       0m 2.05s
----
PY314_ONEDIR-real       0m 2.13s
PY313_ONEDIR-real       0m 2.06s
----
PY314_ONEDIR-real       0m 2.13s
PY313_ONEDIR-real       0m 2.06s
----
PY314_ONEDIR-real       0m 2.12s
PY313_ONEDIR-real       0m 2.05s
----
PY314_ONEDIR-real       0m 2.14s
PY313_ONEDIR-real       0m 2.06s
----
PY314_ONEDIR-real       0m 2.12s
PY313_ONEDIR-real       0m 2.06s
----
PY314_ONEDIR-real       0m 2.13s
PY313_ONEDIR-real       0m 2.07s
----
PY314_ONEDIR-real       0m 2.12s
PY313_ONEDIR-real       0m 2.06s
----
PY314_ONEDIR-real       0m 2.12s
PY313_ONEDIR-real       0m 2.07s
----

So I fired up File Activity Watch and logged what was being read. I've attached the logs. - yt-dlp314_vs._313-FILE_ACTIVITY-report.html.zip

yt-dlp313.exe(just the process) only registers ~22MiB of read, despite having more files overall.

yt-dlp314.exe(just the process) registers almost ~80MiB of read. Why?

I don't mind attaching my binaries, if required.

Thanks for any insight.

[barkoder]

Out of curiosity I also built yt-dlp --onedir using py3.12.12 ,py3.11.14 and py3.10.19 as well.

Here are the benchmarks.

PY314_ONEDIR-real       0m 2.11s
PY313_ONEDIR-real       0m 2.04s
PY312_ONEDIR-real       0m 2.03s
PY311_ONEDIR-real       0m 2.04s
PY310_ONEDIR-real       0m 1.93s
----
PY314_ONEDIR-real       0m 2.11s
PY313_ONEDIR-real       0m 2.04s
PY312_ONEDIR-real       0m 2.06s
PY311_ONEDIR-real       0m 2.04s
PY310_ONEDIR-real       0m 1.92s
----
PY314_ONEDIR-real       0m 2.15s
PY313_ONEDIR-real       0m 2.03s
PY312_ONEDIR-real       0m 2.06s
PY311_ONEDIR-real       0m 2.00s
PY310_ONEDIR-real       0m 1.93s
----
PY314_ONEDIR-real       0m 2.12s
PY313_ONEDIR-real       0m 2.05s
PY312_ONEDIR-real       0m 2.04s
PY311_ONEDIR-real       0m 2.05s
PY310_ONEDIR-real       0m 1.94s
----
PY314_ONEDIR-real       0m 2.13s
PY313_ONEDIR-real       0m 2.02s
PY312_ONEDIR-real       0m 2.02s
PY311_ONEDIR-real       0m 2.03s
PY310_ONEDIR-real       0m 1.94s
----
PY314_ONEDIR-real       0m 2.13s
PY313_ONEDIR-real       0m 2.05s
PY312_ONEDIR-real       0m 2.02s
PY311_ONEDIR-real       0m 2.04s
PY310_ONEDIR-real       0m 1.92s
----
PY314_ONEDIR-real       0m 2.12s
PY313_ONEDIR-real       0m 2.03s
PY312_ONEDIR-real       0m 2.03s
PY311_ONEDIR-real       0m 2.02s
PY310_ONEDIR-real       0m 1.92s
----
PY314_ONEDIR-real       0m 2.09s
PY313_ONEDIR-real       0m 2.03s
PY312_ONEDIR-real       0m 2.02s
PY311_ONEDIR-real       0m 2.02s
PY310_ONEDIR-real       0m 1.93s
----
PY314_ONEDIR-real       0m 2.10s
PY313_ONEDIR-real       0m 2.02s
PY312_ONEDIR-real       0m 2.02s
PY311_ONEDIR-real       0m 2.00s
PY310_ONEDIR-real       0m 1.93s
----
PY314_ONEDIR-real       0m 2.12s
PY313_ONEDIR-real       0m 2.05s
PY312_ONEDIR-real       0m 2.02s
PY311_ONEDIR-real       0m 2.02s
PY310_ONEDIR-real       0m 1.93s
----

YT-DLP ONEDIR PY310 AVERAGE- 1.929s
YT-DLP ONEDIR PY311 AVERAGE- 2.026s
YT-DLP ONEDIR PY312 AVERAGE- 2.032s
YT-DLP ONEDIR PY313 AVERAGE- 2.036s
YT-DLP ONEDIR PY314 AVERAGE- 2.118s

310

• extremely fast, as is to be expected due to its lower size.
• It reads 7 files on first run.
• yt-dlp310.exe(process) registers 13,813.7 KiB of read.

311

• is much slower than 310.
• It also reads 7 files on first run.
• yt-dlp311.exe(process) registers 18,982.1 KiB of read.

312

• is close enough in speed to 311.
• It also reads 7 files on first run.
• yt-dlp312.exe(process) registers 17,680.2 KiB of read.

313

• is close enough in speed to 312 and 311.
• It reads a whopping 64 files on first run. Remarkable that 313's performance is still close enough to 312.
• yt-dlp313.exe(process) registers 22,542.5 KiB of read.

314

• 314 is much slower.
• It reads 36 files on first run.
• yt-dlp314.exe(process) registers a weirdly HUGE 80,549.9 KiB of read.

File activity reports for 310, 311, 312 - yt-dlp310_vs._311_vs._312-FILE_ACTIVITY-report.html.zip

See OP for reports of 313 and 314

[adang1345]

None of my patches would explain an increase in amount read in Python 3.14.0, so this is likely due to some upstream changes in Python 3.14. I would be curious to know whether the same results hold true for the official Python releases.

[barkoder]

I built a yt-dlp onedir using the official 3.14 python on Windows 7.

I had to VxKex-NEXT the official python installer, the installed python.exe, and the built yt-dlp.exe to get it working on Windows 7x64.

yt-dlp314OFFICIAL.exe(process) registers ~73,426 KiB of read. FileActivityWatch report - yt-dlp314OFFICIAL_FILE_ACTIVITY-report.html.zip

I also tried building without upx.exe .
Same result.

Appears to be an issue with 3.14.0 upstream, but I can't be 100% sure about it since I'm on Windows 7, and I had to do a lot of VxKex-ing.

Ideally this test would be run on an officially supported operating system.