Re: [patch] Latency Tracer, voluntary-preempt-2.6.8-rc4-O6

[James Courtier-Dutton]

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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