Messages in this thread | | | Date | Mon, 27 Feb 2006 04:41:40 -0500 | From | Shailabh Nagar <> | Subject | Re: [Patch 2/7] Add sysctl for schedstats |
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Nick Piggin wrote:
<snip>
>> +int schedstats_sysctl_handler(ctl_table *table, int write, struct >> file *filp, >> + void __user *buffer, size_t *lenp, loff_t *ppos) >> +{ >> + int ret, prev = schedstats_sysctl; >> + struct task_struct *g, *t; >> + >> + ret = proc_dointvec(table, write, filp, buffer, lenp, ppos); >> + if ((ret != 0) || (prev == schedstats_sysctl)) >> + return ret; >> + if (schedstats_sysctl) { >> + read_lock(&tasklist_lock); >> + do_each_thread(g, t) { >> + memset(&t->sched_info, 0, sizeof(t->sched_info)); >> + } while_each_thread(g, t); >> + read_unlock(&tasklist_lock); >> + } >> + schedstats_set(schedstats_sysctl); > > > You don't clear the rq's schedstats stuff here.
Good point.
> > And clearing this at all is not really needed for the schedstats > interface. > You have a timestamp and a set of accumulated values, so it is easy to > work > out deltas. So do you need this?
Not clearing the stats will mean userspace has to distinguish between the tasks that are hanging around from before the last turn off, and the ones created after wards. Any delta taken across an interval where schedstats was turned off will give the impression a task was sleeping during the interval (and hence show it had a lesser average wait time than it might actually have experienced).
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