Re: [patch 1/3] basic accounting over taskstats

[Shailabh Nagar <nagar@watson.ibm.com>]

Andrew Morton wrote:

> 
> Or we remove this field altogether, perhaps.  The same info is available
> from /proc/pid/stat anyway.  Is it really needed?
> 

Gathering this data in userspace from /proc might be
difficult esp. for short-lived tasks.

Also, /proc may not be mounted ? I'd heard somewhere that
some sysadmins don't install /proc for security reasons.
Don't know how far thats true.

Several other fields, totalling 58 bytes, added by the CSA
patches are also duplicated in /proc/pid/stat. But all of them
could change in value during the lifetime of a task so I'm
guessing its not useful to get them from /proc
even if some kind of userspace polling of the value was
possible.

But if there is a way, it would sure save a lot of payload
sent over taskstats !

"duplicate" fields from CSA:
+	__u8	ac_nice;		/* task_nice */
+	char	ac_comm[TS_COMM_LEN];	/* Command name */
+	__u8	ac_sched;		/* Scheduling discipline */
+	__u32	ac_pid;			/* Process ID */
+	__u32	ac_ppid;		/* Parent process ID */
+	__u64	ac_utime;		/* User CPU time [usec] */
+	__u64	ac_stime;		/* SYstem CPU time [usec] */
+	__u64	ac_minflt;		/* Minor Page Fault */
+	__u64	ac_majflt;		/* Major Page Fault */