df: improve perfs

[sylvestre]

fixes: #10117

[codspeed-hq]

CodSpeed Performance Report

Merging this PR will not alter performance

_{Comparing sylvestre:df-perf (16b7857) with main (24a8ff0)}

Summary

✅ 142 untouched benchmarks
⏩ 37 skipped benchmarks¹

Footnotes

1. 37 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/timeout/timeout (fails in this run but passes in the 'main' branch)

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/tail/follow-name. tests/tail/follow-name is passing on 'main'. Maybe you have to rebase?
Skipping an intermittent issue tests/tty/tty-eof (passes in this run but fails in the 'main' branch)

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/tail/follow-name. tests/tail/follow-name is passing on 'main'. Maybe you have to rebase?
Skipping an intermittent issue tests/tty/tty-eof (passes in this run but fails in the 'main' branch)
Congrats! The gnu test tests/ls/ls-misc is no longer failing!

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/timeout/timeout (passes in this run but fails in the 'main' branch)

[github-actions]

GNU testsuite comparison:

Skip an intermittent issue tests/shuf/shuf-reservoir (fails in this run but passes in the 'main' branch)
Skip an intermittent issue tests/sort/sort-stale-thread-mem (fails in this run but passes in the 'main' branch)