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SubjectRe: Interesting interaction between lguest and CFS
On 05/06/07, Matt Mackall <mpm@selenic.com> wrote:
> > [...]
> > Click into the lguest window and trigger the delay.
>
> I did:
>
> while true; do sleep 1; cat /proc/sched_debug > sched_debug.txt; done
>
> and got this, hopefully inside the window:
>
> Sched Debug Version: v0.02
> now at 257428593818894 nsecs
>
> cpu: 0
> .nr_running : 3
> .raw_weighted_load : 2063
> .nr_switches : 242830075
> .nr_load_updates : 30172063
> .nr_uninterruptible : 0
> .jiffies : 64282148
> .next_balance : 0
> .curr->pid : 27182
> .clock : 125650217819008823
> .prev_clock_raw : 257428516403535

The delta (clock - prev_clock_raw) looks insane.

The current time (which doesn't depend on rq_clock() --> sched_clock() is
" now at 257428593818894 nsecs " (right at the beginning of the output).

'prev_clock_raw' is updated any time rq_clock() is called - basically
upon any scheduling operation (e.g. enqueue/dequeue)

now - prev_clock_raw == 257428593818894 - 257428516403535 == ~ 80 ms.

while 'clock' reports something crazy.. that would explain why there
wes a huge "block_max" reported earlier.. I guess, sched_clock() is
tsc-based in your case?

Any way to get it switched to jiffies-based one and repeat the test?


--
Best regards,
Dmitry Adamushko
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