* max_clock of the patch "sched_clock: fix cpu_clock()"
@ 2008-09-16 3:01 Lin Ming
2008-09-16 4:48 ` Peter Zijlstra
0 siblings, 1 reply; 2+ messages in thread
From: Lin Ming @ 2008-09-16 3:01 UTC (permalink / raw)
To: Peter Zijlstra; +Cc: linux-kernel
Hi, Peter,
I have a question of the max_clock in below patch,
commit 354879bb977e06695993435745f06a0f6d39ce2b
Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
Date: Mon Aug 25 17:15:34 2008 +0200
sched_clock: fix cpu_clock()
The original code to calculate min_clock and max_clock is,
min_clock = scd->tick_gtod + delta_jiffies * TICK_NSEC;
max_clock = min_clock + TICK_NSEC;
Now it's changed to,
min_clock = wrap_max(scd->tick_gtod, scd->clock);
max_clock = scd->tick_gtod + TICK_NSEC;
Is this max_clock still correct if, in a rare case, irq is disabled for
many ticks?
Thanks,
Lin Ming
^ permalink raw reply [flat|nested] 2+ messages in thread* Re: max_clock of the patch "sched_clock: fix cpu_clock()"
2008-09-16 3:01 max_clock of the patch "sched_clock: fix cpu_clock()" Lin Ming
@ 2008-09-16 4:48 ` Peter Zijlstra
0 siblings, 0 replies; 2+ messages in thread
From: Peter Zijlstra @ 2008-09-16 4:48 UTC (permalink / raw)
To: Lin Ming; +Cc: linux-kernel
On Tue, 2008-09-16 at 11:01 +0800, Lin Ming wrote:
> Hi, Peter,
>
> I have a question of the max_clock in below patch,
> commit 354879bb977e06695993435745f06a0f6d39ce2b
> Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
> Date: Mon Aug 25 17:15:34 2008 +0200
>
> sched_clock: fix cpu_clock()
>
> The original code to calculate min_clock and max_clock is,
> min_clock = scd->tick_gtod + delta_jiffies * TICK_NSEC;
> max_clock = min_clock + TICK_NSEC;
>
> Now it's changed to,
> min_clock = wrap_max(scd->tick_gtod, scd->clock);
> max_clock = scd->tick_gtod + TICK_NSEC;
>
> Is this max_clock still correct if, in a rare case, irq is disabled for
> many ticks?
Nope, it wont (nor would the old), but having irqs disabled for that
long would be something worth fixing.
^ permalink raw reply [flat|nested] 2+ messages in thread
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