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    SubjectRe: [patch] Latency Tracer, voluntary-preempt-2.6.8-rc4-O6
    Ingo Molnar wrote:
    > i've uploaded the latest version of the voluntary-preempt patch:
    >
    > http://redhat.com/~mingo/voluntary-preempt/voluntary-preempt-2.6.8-rc4-O6
    >
    <snip>
    > reports, suggestions welcome,
    >
    > Ingo

    I used O7.

    I have tested this for a day now, and I have noticed problems:
    1)
    kernel syslog gets a record like this:
    > (default.hotplug/1470): 121 us critical section violates 100 us
    threshold.
    > => started at: <kmap_high+0x2b/0x2d0>
    > => ended at: <kmap_high+0x1a9/0x2d0>
    > [<c0105a23>] dump_stack+0x23/0x30
    > [<c0140d14>] check_preempt_timing+0x184/0x1e0
    > [<c0140e84>] sub_preempt_count+0x54/0x5d
    > [<c0152959>] kmap_high+0x1a9/0x2d0
    > [<c017655a>] copy_strings+0xea/0x230
    > [<c01766db>] copy_strings_kernel+0x3b/0x50
    > [<c017840d>] do_execve+0x12d/0x1f0
    > [<c0103284>] sys_execve+0x44/0x80
    > [<c0104b95>] sysenter_past_esp+0x52/0x71
    and the /proc/latency_trace gets:
    > preemption latency trace v1.0
    > -----------------------------
    > latency: 121 us, entries: 1032 (1032)
    > process: default.hotplug/1470, uid: 0
    > nice: -10, policy: 0, rt_priority: 0
    > =======>
    > 0.000ms (+0.000ms): page_address (kmap_high)
    > 0.000ms (+0.000ms): page_slot (page_address)
    > 0.000ms (+0.000ms): flush_all_zero_pkmaps (kmap_high)
    > 0.000ms (+0.000ms): set_page_address (flush_all_zero_pkmaps)
    > [...]
    > 0.118ms (+0.000ms): page_slot (set_page_address)
    > 0.118ms (+0.000ms): check_preempt_timing (sub_preempt_count)

    Could the patch be adjusted to make the syslog and the
    /proc/latency_trace produce the same output?

    2)
    I suspect that there is a problem with reiserfs, but when I detect a
    momentary hang in the system(mouse stops moving), no latency_trace appears.

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