Author nh2
Recipients nh2, pitrou, serhiy.storchaka
Date 2017-12-31.20:11:39
SpamBayes Score -1.0
Marked as misclassified Yes
Message-id <1514751100.61.0.467229070634.issue32453@psf.upfronthosting.co.za>
In-reply-to
Content
It turns out I was wrong when saying that there's some cache we're hitting.

In fact, `rm -r` is still precisely O(n^2), even with the coreutils patch I linked.

Quick overview table of the benchmark:

 nfiles     real   user     sys

 100000    0.51s  0.07s   0.43s
 200000    2.46s  0.15s   0.89s
 400000   10.78s  0.26s   2.21s
 800000   44.72s  0.58s   6.03s
1600000  180.37s  1.06s  10.70s

Each 2x increase of number of files results in 4x increased deletion time.


Full benchmark output:

    # time (mkdir dirtest && cd dirtest && seq 1 100000 | xargs touch)

    real  0m0.722s
    user  0m0.032s
    sys 0m0.680s

    # time rm -rf dirtest/

    real  0m0.519s
    user  0m0.074s
    sys 0m0.437s

    # time (mkdir dirtest && cd dirtest && seq 1 200000 | xargs touch)

    real  0m1.576s
    user  0m0.044s
    sys 0m1.275s

    # time rm -r dirtest/

    real  0m2.469s
    user  0m0.150s
    sys 0m0.890s

    # time (mkdir dirtest && cd dirtest && seq 1 400000 | xargs touch)

    real  0m4.249s
    user  0m0.098s
    sys 0m2.804s

    # time rm -rf dirtest/

    real  0m10.782s
    user  0m0.265s
    sys 0m2.213s

    # time (mkdir dirtest && cd dirtest && seq 1 800000 | xargs touch)

    real  0m10.533s
    user  0m0.204s
    sys 0m5.758s

    # time rm -rf dirtest/

    real  0m44.725s
    user  0m0.589s
    sys 0m6.037s

    # time (mkdir dirtest && cd dirtest && seq 1 1600000 | xargs touch)

    real  0m34.480s
    user  0m0.382s
    sys 0m12.057s

    # time rm -r dirtest/

    real  3m0.371s
    user  0m1.069s
    sys 0m10.704s
History
Date User Action Args
2017-12-31 20:11:40nh2setrecipients: + nh2, pitrou, serhiy.storchaka
2017-12-31 20:11:40nh2setmessageid: <1514751100.61.0.467229070634.issue32453@psf.upfronthosting.co.za>
2017-12-31 20:11:40nh2linkissue32453 messages
2017-12-31 20:11:39nh2create