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

From: Shailabh Nagar
Date: Thu Aug 03 2006 - 09:54:03 EST

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

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 */
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