Messages in this thread | | | Date | Wed, 8 Nov 2006 14:05:10 -0400 | From | "Mauricio Lin" <> | Subject | Jiffies wraparound is not treated in the schedstats |
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Hi Balbir,
Do you know why in the sched_info_arrive() and sched_info_depart() functions the calculation of delta_jiffies does not use the time_after or time_before macro to prevent the miscalculation when jiffies overflow?
For instance the delta_jiffies variable is simply calculated as:
delta_jiffies = now - t->sched_info.last_queued;
Do not you think the more logical way should be
if (time_after(now, t->sched_info.last_queued)) delta_jiffies = now - t->sched_info.last_queued; else delta_jiffies = (MAX_JIFFIES - t->sched_info.last_queued) + now
I have included more variables to measure some issues of schedule in the kernel (following schedstat idea) and I noticed that jiffies wraparound has led to wrong values, since the user space tool when collecting the values is producing negative values.
Any comments?
Can I provide a patch for that?
BR,
Mauricio Lin. - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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