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SubjectRe: [PATCH] proc/schedstat: Expose /proc/<pid>/schedstat if delay accounting is enabled
On 2015/05/29 10:04AM, Ingo Molnar wrote:
>
> * Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com> wrote:
>
> > /proc/<pid>/schedstat is currently only available if CONFIG_SCHEDSTATS is
> > enabled. But, all the fields that this exposes are available and valid
> > if CONFIG_TASK_DELAY_ACCT is enabled as well.
> >
> > Signed-off-by: Naveen N. Rao <naveen.n.rao@linux.vnet.ibm.com>
> > ---
> > fs/proc/base.c | 11 +++++++----
> > 1 file changed, 7 insertions(+), 4 deletions(-)
> >
> > diff --git a/fs/proc/base.c b/fs/proc/base.c
> > index 093ca14..3ece303 100644
> > --- a/fs/proc/base.c
> > +++ b/fs/proc/base.c
> > @@ -304,14 +304,17 @@ static int proc_pid_stack(struct seq_file *m, struct pid_namespace *ns,
> > }
> > #endif
> >
> > +#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
> > +#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
> > +#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
>

Hi Ingo,
Thanks for the review.

> So such #ifdef parades are ugly and are usually a sign of some problem with the
> patch - as in this case.
>
> But there's deeper problems as well:
>
> /*
> * Provides /proc/PID/schedstat
> */
> static int proc_pid_schedstat(struct seq_file *m, struct pid_namespace *ns,
> struct pid *pid, struct task_struct *task)
> {
> seq_printf(m, "%llu %llu %lu\n",
> (unsigned long long)task->se.sum_exec_runtime,
> (unsigned long long)task->sched_info.run_delay,
> task->sched_info.pcount);
>
> return 0;
> }
>
> - The sum_exec_runtime field is available unconditionally.
>
> - But the sched_info.run_delay field is only maintained if CONFIG_SCHEDSTATS is
> enabled.
>
> - Also, the sched_info.pcount field is again only maintained if CONFIG_SCHEDSTATS
> is enabled.

I may be missing something, but from my reading of the code, the above
are maintained if any one of CONFIG_SCHEDSTATS or CONFIG_TASK_DELAY_ACCT
are enabled (from kernel/sched/stats.h).

Only the runqueue-specific sched_info is tracked with CONFIG_SCHEDSTATS
separately [kernel/sched/stats.c and the corresponding global
/proc/schedstat]


Regards,
Naveen



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