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    SubjectRe: [RFC][PATCH 0/5] uts namespaces: Introduction
    Serge,

    > This patchset is based on Kirill Korotaev's Mar 24 submission, taking
    > comments (in particular from James Morris and Eric Biederman) into
    > account.
    thanks a lot for doing this!

    > Some performance results are attached. I was mainly curious whether
    > it would be worth putting the task_struct->uts_ns pointer inside
    > a #ifdef CONFIG_UTS_NS. The result show that leaving it in when
    > CONFIG_UTS_NS=n has negligable performance impact, so that is the
    > approach this patch takes.
    Serge, your testing approach looks really strange for me.
    First of all, you selected the worst namespace to check performance
    overhead on.
    1) uts_ns is rarely used and never used on hot paths,
    2) also all these test suites below doesn't test the code paths you
    modified.

    So I wonder what was the goal of these tests, especially dbench?!

    Thanks,
    Kirill

    >
    > -serge
    >
    > Performance testing was done on a 2-cpu hyperthreaded
    > x86 box with 16G ram. The following tests were run:
    > dbench (20 times, four clients, on reiser fs non-isolated partition)
    > tbench (20 times, 5 connections)
    > kernbench (20 times)
    > reaim (20 times ranging from 1 to 15 users)
    >
    > They were run on 2.6.17-rc1:
    > pristine
    > patched, but with !CONFIG_UTS_NS ("disabled")
    > patched with CONFIG_UTS_NS=y ("enabled")
    >
    > All results are presented as means +/- 95% confidence interval.
    >
    > Dbench results:
    > pristine: 387.080727 +/- 9.344585
    > patched disabled: 389.524364 +/- 9.574921
    > patched enabled: 370.155600 +/- 30.127808
    >
    > Tbench results:
    > pristine: 388.940100 +/- 18.095104
    > patched disabled: 389.173700 +/- 23.658035
    > patched enabled: 394.333200 +/- 25.813393
    >
    > Kernbench results:
    > pristine: 70.317500 +/- 0.210833
    > patched, disabled: 70.860000 +/- 0.179292
    > patched, enabled: 70.346500 +/- 0.184784
    >
    > Reaim results:
    > pristine:
    > Nclients Mean 95% CI
    > 1 106080.000000 11327.896029
    > 3 236057.142000 18205.544810
    > 5 247867.136000 23536.800062
    > 7 265370.000000 21284.335743
    > 9 262969.936000 18225.497529
    > 11 278256.000000 6230.342816
    > 13 284288.016000 8924.589388
    > 15 286987.170000 7881.034658
    >
    > patched, disabled:
    > Nclients Mean 95% CI
    > 1 105400.000000 8739.978241
    > 3 229500.000000 0.000000
    > 5 252325.176667 16685.663423
    > 7 265125.000000 6747.777319
    > 9 271258.645000 11715.635212
    > 11 280662.608333 7775.229351
    > 13 277719.706667 8173.390359
    > 15 278515.421667 10963.211450
    >
    > patched, enabled:
    > Nclients Mean 95% CI
    > 1 102000.000000 0.000000
    > 3 224400.000000 14159.870036
    > 5 242963.288000 40529.490781
    > 7 255150.000000 8745.802081
    > 9 270154.284000 8918.863136
    > 11 283134.260000 12239.361252
    > 13 288497.540000 11336.550964
    > 15 280022.728000 8804.882369
    >
    >


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