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    SubjectKernel marker has no performance impact on ia64.
    Hello,

    I evaluated overhead of kernel marker using linux-2.6-sched-fixes
    git tree, which includes several markers for LTTng, using an ia64
    server.

    While the immediate trace mark feature isn't implemented on ia64,
    there is no major performance regression. So, I think that we
    don't have any issues to propose merging marker point patches
    into Linus's tree from the viewpoint of performance impact.

    I prepared two kernels to evaluate. The first one was compiled
    without CONFIG_MARKERS. The second one was enabled CONFIG_MARKERS.

    I downloaded the original hackbench from the following URL:
    http://devresources.linux-foundation.org/craiger/hackbench/src/hackbench.c

    I ran hackbench 5 times in each condition and calculated the
    average and difference between the kernels.

    The parameter of hackbench: every 50 from 50 to 800
    The number of CPUs of the server: 2, 4, and 8

    Below is the results. As you can see, major performance
    regression wasn't found in any case. Even if number of processes
    increases, differences between marker-enabled kernel and marker-
    disabled kernel doesn't increase. Moreover, if number of CPUs
    increases, the differences doesn't increase either.

    Curiously, marker-enabled kernel is better than marker-disabled
    kernel in more than half cases, although I guess it comes from
    the difference of memory access pattern.


    * 2 CPUs

    Number of | without | with | diff | diff |
    processes | Marker [Sec] | Marker [Sec] | [Sec] | [%] |
    --------------------------------------------------------------
    50 | 4.811 | 4.872 | +0.061 | +1.27 |
    100 | 9.854 | 10.309 | +0.454 | +4.61 |
    150 | 15.602 | 15.040 | -0.562 | -3.6 |
    200 | 20.489 | 20.380 | -0.109 | -0.53 |
    250 | 25.798 | 25.652 | -0.146 | -0.56 |
    300 | 31.260 | 30.797 | -0.463 | -1.48 |
    350 | 36.121 | 35.770 | -0.351 | -0.97 |
    400 | 42.288 | 42.102 | -0.186 | -0.44 |
    450 | 47.778 | 47.253 | -0.526 | -1.1 |
    500 | 51.953 | 52.278 | +0.325 | +0.63 |
    550 | 58.401 | 57.700 | -0.701 | -1.2 |
    600 | 63.334 | 63.222 | -0.112 | -0.18 |
    650 | 68.816 | 68.511 | -0.306 | -0.44 |
    700 | 74.667 | 74.088 | -0.579 | -0.78 |
    750 | 78.612 | 79.582 | +0.970 | +1.23 |
    800 | 85.431 | 85.263 | -0.168 | -0.2 |
    --------------------------------------------------------------

    * 4 CPUs

    Number of | without | with | diff | diff |
    processes | Marker [Sec] | Marker [Sec] | [Sec] | [%] |
    --------------------------------------------------------------
    50 | 2.586 | 2.584 | -0.003 | -0.1 |
    100 | 5.254 | 5.283 | +0.030 | +0.56 |
    150 | 8.012 | 8.074 | +0.061 | +0.76 |
    200 | 11.172 | 11.000 | -0.172 | -1.54 |
    250 | 13.917 | 14.036 | +0.119 | +0.86 |
    300 | 16.905 | 16.543 | -0.362 | -2.14 |
    350 | 19.901 | 20.036 | +0.135 | +0.68 |
    400 | 22.908 | 23.094 | +0.186 | +0.81 |
    450 | 26.273 | 26.101 | -0.172 | -0.66 |
    500 | 29.554 | 29.092 | -0.461 | -1.56 |
    550 | 32.377 | 32.274 | -0.103 | -0.32 |
    600 | 35.855 | 35.322 | -0.533 | -1.49 |
    650 | 39.192 | 38.388 | -0.804 | -2.05 |
    700 | 41.744 | 41.719 | -0.025 | -0.06 |
    750 | 45.016 | 44.496 | -0.520 | -1.16 |
    800 | 48.212 | 47.603 | -0.609 | -1.26 |
    --------------------------------------------------------------

    * 8 CPUs

    Number of | without | with | diff | diff |
    processes | Marker [Sec] | Marker [Sec] | [Sec] | [%] |
    --------------------------------------------------------------
    50 | 2.094 | 2.072 | -0.022 | -1.07 |
    100 | 4.162 | 4.273 | +0.111 | +2.66 |
    150 | 6.485 | 6.540 | +0.055 | +0.84 |
    200 | 8.556 | 8.478 | -0.078 | -0.91 |
    250 | 10.458 | 10.258 | -0.200 | -1.91 |
    300 | 12.425 | 12.750 | +0.325 | +2.62 |
    350 | 14.807 | 14.839 | +0.032 | +0.22 |
    400 | 16.801 | 16.959 | +0.158 | +0.94 |
    450 | 19.478 | 19.009 | -0.470 | -2.41 |
    500 | 21.296 | 21.504 | +0.208 | +0.98 |
    550 | 23.842 | 23.979 | +0.137 | +0.57 |
    600 | 26.309 | 26.111 | -0.198 | -0.75 |
    650 | 28.705 | 28.446 | -0.259 | -0.9 |
    700 | 31.233 | 31.394 | +0.161 | +0.52 |
    750 | 34.064 | 33.720 | -0.344 | -1.01 |
    800 | 36.320 | 36.114 | -0.206 | -0.57 |
    --------------------------------------------------------------

    Best regards,
    Hideo


    P.S. When I compiled the linux-2.6-sched-fixes tree on ia64, I
    had to revert the following git commit since pteval_t is defined
    on x86 only.

    commit 8686f2b37e7394b51dd6593678cbfd85ecd28c65
    Date: Tue May 6 15:42:40 2008 -0700

    generic, x86, PAT: fix mprotect

    --
    Hitachi Computer Products (America) Inc.


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