[PATCH] per-task-delay-accounting: taskstats interface

Create a "taskstats" interface based on generic netlink (NETLINK_GENERIC
family), for getting statistics of tasks and thread groups during their
lifetime and when they exit.  The interface is intended for use by multiple
accounting packages though it is being created in the context of delay
accounting.

This patch creates the interface without populating the fields of the data
that is sent to the user in response to a command or upon the exit of a task.
Each accounting package interested in using taskstats has to provide an
additional patch to add its stats to the common structure.

[akpm@osdl.org: cleanups, Kconfig fix]
Signed-off-by: Shailabh Nagar <nagar@us.ibm.com>
Signed-off-by: Balbir Singh <balbir@in.ibm.com>
Cc: Jes Sorensen <jes@sgi.com>
Cc: Peter Chubb <peterc@gelato.unsw.edu.au>
Cc: Erich Focht <efocht@ess.nec.de>
Cc: Levent Serinol <lserinol@gmail.com>
Cc: Jay Lan <jlan@engr.sgi.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

init/Kconfig

@@ -158,6 +158,19 @@ config BSD_PROCESS_ACCT_V3
 	  for processing it. A preliminary version of these tools is available
 	  at <http://www.physik3.uni-rostock.de/tim/kernel/utils/acct/>.
 
+config TASKSTATS
+	bool "Export task/process statistics through netlink (EXPERIMENTAL)"
+	depends on NET
+	default n
+	help
+	  Export selected statistics for tasks/processes through the
+	  generic netlink interface. Unlike BSD process accounting, the
+	  statistics are available during the lifetime of tasks/processes as
+	  responses to commands. Like BSD accounting, they are sent to user
+	  space on task exit.
+
+	  Say N if unsure.
+
 config TASK_DELAY_ACCT
 	bool "Enable per-task delay accounting (EXPERIMENTAL)"
 	help

init/main.c

@@ -41,6 +41,7 @@
 #include <linux/cpu.h>
 #include <linux/cpuset.h>
 #include <linux/efi.h>
+#include <linux/taskstats_kern.h>
 #include <linux/delayacct.h>
 #include <linux/unistd.h>
 #include <linux/rmap.h>
@@ -575,6 +576,7 @@ asmlinkage void __init start_kernel(void)
 	proc_root_init();
 #endif
 	cpuset_init();
+	taskstats_init_early();
 	delayacct_init();
 
 	check_bugs();