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SubjectRe: [PATCH] proc/schedstat: Expose /proc/<pid>/schedstat if delay accounting is enabled

* 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)

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.

So the claim in your changelog that these fields are maintained in the
delayaccounting case is plain false: none of the fields are conditional on delay
accounting.

So what's the purpose of your patch?

Thanks,

Ingo


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