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tee: own page caches using memfd for 2+ outputs - #15854

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tee: own page caches using memfd for 2+ outputs#15854
oech3 wants to merge 1 commit into
uutils:mainfrom
oech3:tee-memfd

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@oech3 oech3 commented Oct 26, 2026 •
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Closes #15803 .
Note that this causes large performance drop:

> yes|tee /dev/null|pv>/dev/null
 133GiB 0:00:02 [66.8GiB/s]
> yes|tee-memfd /dev/null|pv>/dev/null
17.7GiB 0:00:02 [8.86GiB/s]
> yes|tee-rw /dev/null|pv>/dev/null
10.1GiB 0:00:02 [5.09GiB/s]

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github-actions Bot commented Oct 26, 2026 •
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GNU testsuite comparison:

GNU test failed: tests/tee/tee. tests/tee/tee is passing on 'main'. Maybe you have to rebase?

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oech3 force-pushed the tee-memfd branch 4 times, most recently from 5681e0d to e0a00ac Compare October 26, 2026 04:24
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oech3 commented Oct 26, 2026

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We were bypassing (thus, incorrectly passing) write-eagain.sh. Reviewer can ignore it. Needs investigation for tee.sh.

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oech3 marked this pull request as draft October 26, 2026 04:36
@oech3 oech3 changed the title tee: restrict fast-path to 1 output tee: own page caches using memfd for 2+ outputs Oct 26, 2026
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oech3 force-pushed the tee-memfd branch 8 times, most recently from 934d157 to 40d7a1c Compare October 26, 2026 08:32
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oech3 force-pushed the tee-memfd branch 3 times, most recently from 77d41f4 to b860187 Compare October 26, 2026 09:46
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oech3 marked this pull request as ready for review October 26, 2026 09:46
oech3
oech3 commented Oct 26, 2026
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Comment thread tests/by-util/test_tee.rs
}

#[test]
#[ignore = "this test was made when we were not using memfd which accidentally gets EFBIG. Needed to rewrite to exclude memfd."]

@oech3 oech3 Oct 26, 2026

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@abendrothj Is there any way to exclude memfd from rlimit?

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tee: zero-copy lets stdout and FILE differ if input changes after tee exits

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