linux-kernel - Re: [PATCH] proc/schedstat: Expose /proc/<pid>/schedstat if delay accounting is enabled

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Date:	Fri, 29 May 2015 15:15:47 +0530
From:	"Naveen N. Rao" <naveen.n.rao@...ux.vnet.ibm.com>
To:	Ingo Molnar <mingo@...nel.org>
Cc:	Balbir Singh <bsingharora@...il.com>,
	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	srikar@...ux.vnet.ibm.com
Subject: Re: [PATCH] proc/schedstat: Expose /proc/<pid>/schedstat if delay
 accounting is enabled

On 2015/05/29 11:18AM, Ingo Molnar wrote:
> 
> * Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com> wrote:
> 
> > On 2015/05/29 10:04AM, Ingo Molnar wrote:
> > > 
> > > * Naveen N. Rao <naveen.n.rao@...ux.vnet.ibm.com> wrote:
> > > 
> > >  - 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).
> 
> Hm, indeed - I mis-read the rq-specific code - sorry.
> 
> So all this should really be cleaned up:
> 
> include/linux/sched.h:#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
> include/linux/sched.h:#endif /* defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT) */
> include/linux/sched.h:#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
> kernel/sched/core.c:#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
> kernel/sched/stats.h:#if defined(CONFIG_SCHEDSTATS) || defined(CONFIG_TASK_DELAY_ACCT)
> kernel/sched/stats.h:#endif /* CONFIG_SCHEDSTATS || CONFIG_TASK_DELAY_ACCT */
> 
> by introducing an intermediate Kconfig variable, named CONFIG_SCHED_INFO or so, 
> and selected by both SCHEDSTATS and TASK_DELAY_ACCT.
> 
> Please make it two patches: the first one adds CONFIG_SCHED_INFO and cleans up the 
> code to use it, the second one uses it for the procps change.

Sure, will do.

On a related note, even though sum_exec_runtime is available 
unconditionally, I dump all zeroes in my patch if !sched_info_on() to 
make it clear that some of the fields are not available. Is this ok or 
should be display sum_exec_runtime regardless of sched_info?

Thanks,
Naveen

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