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

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Date:	Fri, 29 May 2015 22:36:00 +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 11:54AM, Ingo Molnar wrote:
> 
> > > 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?
> 
> So I'd suggest printing -1 for non-available fields, that should be unambigous 
> enough and makes it also possible to write out 0 in some cases.

Per Documentation/scheduler/sched-stats.txt (and the linked latency.c 
there), user-space seems to be expecting unsigned values here. Would 
displaying -1 here be ok?


Thanks,
Naveen

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