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    Subject[patch 00/18] CFS Bandwidth Control v7.2
    Hi all,

    Please find attached the incremental v7.2 for bandwidth control.

    This release follows a fairly intensive period of scraping cycles across
    various configurations. Unfortunately we seem to be currently taking an IPC
    hit for jump_labels (despite a savings in branches/instr. ret) which despite
    fairly extensive digging I don't have a good explanation for. The emitted
    assembly /looks/ ok, but cycles/wall time is consistently higher across several
    platforms.

    As such I've demoted the jumppatch to [RFT] while these details are worked
    out. But there's no point in holding up the rest of the series any more.

    [ Please find the specific discussion related to the above attached to patch
    17/18. ]

    So -- without jump labels -- the current performance looks like:

    instructions cycles branches
    ---------------------------------------------------------------------------------------------
    clovertown [!BWC] 843695716 965744453 151224759
    +unconstrained 845934117 (+0.27) 974222228 (+0.88) 152715407 (+0.99)
    +10000000000/1000: 855102086 (+1.35) 978728348 (+1.34) 154495984 (+2.16)
    +10000000000/1000000: 853981660 (+1.22) 976344561 (+1.10) 154287243 (+2.03)

    barcelona [!BWC] 810514902 761071312 145351489
    +unconstrained 820573353 (+1.24) 748178486 (-1.69) 148161233 (+1.93)
    +10000000000/1000: 827963132 (+2.15) 757829815 (-0.43) 149611950 (+2.93)
    +10000000000/1000000: 827701516 (+2.12) 753575001 (-0.98) 149568284 (+2.90)

    westmere [!BWC] 792513879 702882443 143267136
    +unconstrained 802533191 (+1.26) 694415157 (-1.20) 146071233 (+1.96)
    +10000000000/1000: 809861594 (+2.19) 701781996 (-0.16) 147520953 (+2.97)
    +10000000000/1000000: 809752541 (+2.18) 705278419 (+0.34) 147502154 (+2.96)

    Under the workload:
    mkdir -p /cgroup/cpu/test
    echo $$ > /dev/cgroup/cpu/test (only cpu,cpuacct mounted)
    (W1) taskset -c 0 perf stat --repeat 50 -e instructions,cycles,branches bash -c "for ((i=0;i<5;i++)); do $(dirname $0)/pipe-test 20000; done"

    This may seem a strange work-load but it works around some bizarro overheads
    currently introduced by perf. Comparing for example with::w
    (W2)taskset -c 0 perf stat --repeat 50 -e instructions,cycles,branches bash -c "$(dirname $0)/pipe-test 100000;true"
    (W3)taskset -c 0 perf stat --repeat 50 -e instructions,cycles,branches bash -c "$(dirname $0)/pipe-test 100000;"


    We see:
    (W1) westmere [!BWC] 792513879 702882443 143267136 0.197246943
    (W2) westmere [!BWC] 912241728 772576786 165734252 0.214923134
    (W3) westmere [!BWC] 904349725 882084726 162577399 0.748506065

    vs an 'ideal' total exec time of (approximately):
    $ time taskset -c 0 ./pipe-test 100000
    real 0m0.198 user 0m0.007s ys 0m0.095s

    The overhead in W2 is explained by that invoking pipe-test directly, one of
    the siblings is becoming the perf_ctx parent, invoking lots of pain every time
    we switch. I do not have a reasonable explantion as to why (W1) is so much
    cheaper than (W2), I stumbled across it by accident when I was trying some
    combinations to reduce the <perf stat>-to-<perf stat> variance.

    v7.2
    -----------
    - Build errors in !CGROUP_SCHED case fixed
    - !CONFIG_SMP now 'supported' (#ifdef munging)
    - gcc was failing to inline account_cfs_rq_runtime, affecting performance
    - checks in expire_cfs_rq_runtime() and check_enqueue_throttle() re-organized
    to save branches.
    - jump labels introduced in the case BWC is not being used system-wide to
    reduce inert overhead.
    - branch saved in expiring runtime (reorganize conditonals)

    Hidetoshi, the following patchsets have changed enough to necessitate tweaking
    of your Reviewed-by:
    [patch 09/18] sched: add support for unthrottling group entities (extensive)
    [patch 11/18] sched: prevent interactions with throttled entities (update_cfs_shares)
    [patch 12/18] sched: prevent buddy interactions with throttled entities (new)


    Previous postings:
    -----------------
    v7.1: https://lkml.org/lkml/2011/7/7/24
    v7: http://lkml.org/lkml/2011/6/21/43
    v6: http://lkml.org/lkml/2011/5/7/37
    v5: http://lkml.org/lkml/2011/3 /22/477
    v4: http://lkml.org/lkml/2011/2/23/44
    v3: http://lkml.org/lkml/2010/10/12/44
    v2: http://lkml.org/lkml/2010/4/28/88
    Original posting: http://lkml.org/lkml/2010/2/12/393

    Prior approaches: http://lkml.org/lkml/2010/1/5/44 ["CFS Hard limits v5"]

    Thanks,

    - Paul



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