per-task-delay-accounting: update document and getdelays.c for memory reclaim

Update document and make getdelays.c show delay accounting for memory reclaim.

For making a distinction between "swapping in pages" and "memory reclaim"
in getdelays.c, MEM is changed to SWAP.

Signed-off-by: Keika Kobayashi <kobayashi.kk@ncos.nec.co.jp>
Acked-by: Balbir Singh <balbir@linux.vnet.ibm.com>
Cc: KOSAKI Motohiro <kosaki.motohiro@jp.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Documentation/accounting/delay-accounting.txt

@@ -11,6 +11,7 @@ the delays experienced by a task while
 a) waiting for a CPU (while being runnable)
 b) completion of synchronous block I/O initiated by the task
 c) swapping in pages
+d) memory reclaim
 
 and makes these statistics available to userspace through
 the taskstats interface.
@@ -41,7 +42,7 @@ this structure. See
      include/linux/taskstats.h
 for a description of the fields pertaining to delay accounting.
 It will generally be in the form of counters returning the cumulative
-delay seen for cpu, sync block I/O, swapin etc.
+delay seen for cpu, sync block I/O, swapin, memory reclaim etc.
 
 Taking the difference of two successive readings of a given
 counter (say cpu_delay_total) for a task will give the delay
@@ -94,7 +95,9 @@ CPU	count	real total	virtual total	delay total
 	7876	92005750	100000000	24001500
 IO	count	delay total
 	0	0
-MEM	count	delay total
+SWAP	count	delay total
+	0	0
+RECLAIM	count	delay total
 	0	0
 
 Get delays seen in executing a given simple command
@@ -108,5 +111,7 @@ CPU	count	real total	virtual total	delay total
 	6	4000250		4000000		0
 IO	count	delay total
 	0	0
-MEM	count	delay total
+SWAP	count	delay total
+	0	0
+RECLAIM	count	delay total
 	0	0

Documentation/accounting/getdelays.c

@@ -196,14 +196,18 @@ void print_delayacct(struct taskstats *t)
 	       "      %15llu%15llu%15llu%15llu\n"
 	       "IO    %15s%15s\n"
 	       "      %15llu%15llu\n"
-	       "MEM   %15s%15s\n"
+	       "SWAP  %15s%15s\n"
+	       "      %15llu%15llu\n"
+	       "RECLAIM  %12s%15s\n"
 	       "      %15llu%15llu\n",
 	       "count", "real total", "virtual total", "delay total",
 	       t->cpu_count, t->cpu_run_real_total, t->cpu_run_virtual_total,
 	       t->cpu_delay_total,
 	       "count", "delay total",
 	       t->blkio_count, t->blkio_delay_total,
-	       "count", "delay total", t->swapin_count, t->swapin_delay_total);
+	       "count", "delay total", t->swapin_count, t->swapin_delay_total,
+	       "count", "delay total",
+	       t->freepages_count, t->freepages_delay_total);
 }
 
 void task_context_switch_counts(struct taskstats *t)