MobileRead Forums - View Single Post - Calibre taking 30+ minutes to start with 20K book library

Luna · Yesterday, 08:06 AM

Hello! I'm new here. I can't believe I didn't know about this website and forum!

I posted on Reddit because I had a problem with Calibre and was advised to post it here as well. I have found what causes the problem (and a temporary fix for it) but I don't know WHY it happens. Maybe someone here can help me figure it out?

If there is anything you want to know about my set-up or if you want me to test anything, please let me know!

I will post what I posted on Reddit, because that has all the details:

Start of Reddit post

I'm experiencing extreme startup times with Calibre (8.13.0, now upgraded to 8.14) on macOS 26.1. Opening my library of 20K+ books takes 30+ minutes, often appearing to hang completely before eventually loading.

What works normally:

Small test libraries (5-10 books) open instantly
The library itself is healthy, "Check Library" finds no errors
Database integrity check passes (PRAGMA integrity_check = ok)
Database size is normal (29MB for 20K books)

What I've tested without success:

Starting with --ignore-plugins : fast startup
Disabling all user-installed plugins: still slow
Disabling device detection and content server: still slow
Complete network disconnect (WiFi + Ethernet off): still slow
VACUUM on database: no improvement
Fresh Calibre install with clean config: still slow
Different DNS servers (already using 8.8.8.8)

System:

iMac 2020, 72GB RAM, macOS 26.1 with 20GB library, 63K files, 29MB database
No custom columns, no saved searches
Standard metadata plugins only
Library on internal SSD (not network)

The fact that --ignore-plugins makes it fast suggests a built-in plugin or initialization routine is the culprit, but I can't identify which one.

Has anyone experienced similar issues with large libraries? Any suggestions for further troubleshooting? Thanks in advance!

EDIT (of Reddit post): SOLVED!
Solved meaning I know what's causing the problem and what to do about it, but I still don't know WHY it is happening.

After lots and lots of troubleshooting, I found the following (with a little help from Claude and ChatGPT &#128521

:

Calibre took 30+ minutes to start with my 20K+ library, using 46GB RAM (!) and pegging CPU at 100%.

Root Cause: Corrupt/problematic cache folders created during runtime:
~/Library/Caches/calibre/aa/
~/Library/Caches/calibre/ev2/
~/Library/Caches/calibre/gui-thumbnail-cache/
~/Library/Caches/calibre/qwe/

These remain after quit and cause the next startup to hang with Text Services Manager (TSM) failures and massive memory leaks.

TSMSendMessageToUIServer: CFMessagePortSendRequest FAILED(-1)

With 20K+ books = 20K+ failed calls = massive delays + memory leak.

If it happens again:

killall calibre 2>/dev/null
rm -rf ~/Library/Caches/calibre/* /tmp/calibre-* 2>/dev/null
sleep 2
/Applications/calibre.app/Contents/MacOS/calibre

And if the problem persists, reset TSM:

sudo rm -rf /System/Library/Caches/com.apple.IntlDataCache*
sudo rm -rf /var/folders/*/*/*/com.apple.IntlDataCache*
sudo reboot

Startup now takes a few seconds instead of 30+ minutes!

End of Reddit post.

Any help or input is very much appreciated! Thanks in advance!

Yesterday, 08:06 AM	#1
Luna Junior Member Posts: 4 Karma: 10 Join Date: Nov 2025 Device: Kindle Voyage	Calibre taking 30+ minutes to start with 20K book library Hello! I'm new here. I can't believe I didn't know about this website and forum! I posted on Reddit because I had a problem with Calibre and was advised to post it here as well. I have found what causes the problem (and a temporary fix for it) but I don't know WHY it happens. Maybe someone here can help me figure it out? If there is anything you want to know about my set-up or if you want me to test anything, please let me know! I will post what I posted on Reddit, because that has all the details: *Start of Reddit post* I'm experiencing extreme startup times with Calibre (8.13.0, now upgraded to 8.14) on macOS 26.1. Opening my library of 20K+ books takes 30+ minutes, often appearing to hang completely before eventually loading. What works normally: Small test libraries (5-10 books) open instantly The library itself is healthy, "Check Library" finds no errors Database integrity check passes (PRAGMA integrity_check = ok) Database size is normal (29MB for 20K books) What I've tested without success: Starting with --ignore-plugins : fast startup Disabling all user-installed plugins: still slow Disabling device detection and content server: still slow Complete network disconnect (WiFi + Ethernet off): still slow VACUUM on database: no improvement Fresh Calibre install with clean config: still slow Different DNS servers (already using 8.8.8.8) System: iMac 2020, 72GB RAM, macOS 26.1 with 20GB library, 63K files, 29MB database No custom columns, no saved searches Standard metadata plugins only Library on internal SSD (not network) The fact that --ignore-plugins makes it fast suggests a built-in plugin or initialization routine is the culprit, but I can't identify which one. Has anyone experienced similar issues with large libraries? Any suggestions for further troubleshooting? Thanks in advance! EDIT (of Reddit post): SOLVED! Solved meaning I know what's causing the problem and what to do about it, but I still don't know WHY it is happening. After lots and lots of troubleshooting, I found the following (with a little help from Claude and ChatGPT &#128521: Calibre took 30+ minutes to start with my 20K+ library, using 46GB RAM (!) and pegging CPU at 100%. Root Cause: Corrupt/problematic cache folders created during runtime: ~/Library/Caches/calibre/aa/ ~/Library/Caches/calibre/ev2/ ~/Library/Caches/calibre/gui-thumbnail-cache/ ~/Library/Caches/calibre/qwe/ These remain after quit and cause the next startup to hang with Text Services Manager (TSM) failures and massive memory leaks. TSMSendMessageToUIServer: CFMessagePortSendRequest FAILED(-1) With 20K+ books = 20K+ failed calls = massive delays + memory leak. If it happens again: killall calibre 2>/dev/null rm -rf ~/Library/Caches/calibre/* /tmp/calibre-* 2>/dev/null sleep 2 /Applications/calibre.app/Contents/MacOS/calibre And if the problem persists, reset TSM: sudo rm -rf /System/Library/Caches/com.apple.IntlDataCache* sudo rm -rf /var/folders////com.apple.IntlDataCache sudo reboot Startup now takes a few seconds instead of 30+ minutes! *End of Reddit post.* Any help or input is very much appreciated! Thanks in advance!