Emacs 29 master
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Empty ‘directory-abbrev-alist’
Local | Elapsed time: 0.082094s (0.012981s in 1 GCs)
Tramp | Elapsed time: 0.570441s (0.175013s in 13 GCs)

100 items in ‘directory-abbrev-alist’ (no matches)
Local | Elapsed time: 0.334320s (0.129351s in 10 GCs)
Tramp | Elapsed time: 0.838366s (0.294330s in 22 GCs)

100 items in ‘directory-abbrev-alist’ (all matches)
Local | Elapsed time: 0.530187s (0.320165s in 25 GCs)
Tramp | Elapsed time: 0.836190s (0.285371s in 22 GCs)

500 items in ‘directory-abbrev-alist’ (no matches)
Local | Elapsed time: 1.089229s (0.492225s in 38 GCs)
Tramp | Elapsed time: 1.587351s (0.649014s in 50 GCs)

500 items in ‘directory-abbrev-alist’ (all matches)
Local | Elapsed time: 1.292103s (0.687631s in 53 GCs)
Tramp | Elapsed time: 1.592210s (0.651090s in 50 GCs)


With old patch (from Nov 13)
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Empty ‘directory-abbrev-alist’
Local | Elapsed time: 0.076136s (0.012949s in 1 GCs)
Tramp | Elapsed time: 0.510445s (0.160052s in 12 GCs)

100 items in ‘directory-abbrev-alist’ (no matches)
Local | Elapsed time: 0.342509s (0.130916s in 10 GCs)
Tramp | Elapsed time: 0.780201s (0.281118s in 21 GCs)

100 items in ‘directory-abbrev-alist’ (all matches)
Local | Elapsed time: 0.538353s (0.323898s in 25 GCs)
Tramp | Elapsed time: 0.699262s (0.245942s in 19 GCs)

500 items in ‘directory-abbrev-alist’ (no matches)
Local | Elapsed time: 1.104786s (0.500880s in 38 GCs)
Tramp | Elapsed time: 1.524662s (0.642236s in 49 GCs)

500 items in ‘directory-abbrev-alist’ (all matches)
Local | Elapsed time: 1.299160s (0.687867s in 53 GCs)
Tramp | Elapsed time: 1.519829s (0.651691s in 47 GCs)


With new patch (from Nov 14)
----------------------------

Empty ‘directory-abbrev-alist’
Local | Elapsed time: 0.077384s (0.013098s in 1 GCs)
Tramp | Elapsed time: 0.839370s (0.267310s in 20 GCs)

100 items in ‘directory-abbrev-alist’ (no matches)
Local | Elapsed time: 0.338255s (0.131483s in 10 GCs)
Tramp | Elapsed time: 1.084413s (0.370287s in 28 GCs)

100 items in ‘directory-abbrev-alist’ (all matches)
Local | Elapsed time: 0.546285s (0.333527s in 25 GCs)
Tramp | Elapsed time: 1.038340s (0.359871s in 27 GCs)

500 items in ‘directory-abbrev-alist’ (no matches)
Local | Elapsed time: 1.099473s (0.500838s in 38 GCs)
Tramp | Elapsed time: 1.848707s (0.747623s in 56 GCs)

500 items in ‘directory-abbrev-alist’ (all matches)
Local | Elapsed time: 1.313968s (0.704238s in 53 GCs)
Tramp | Elapsed time: 1.802593s (0.727102s in 55 GCs)