perf kmem: Add help file

Add Documentation/perf-kmem.txt
Signed-off-by: NLi Zefan <lizf@cn.fujitsu.com>
Acked-by: NPekka Enberg <penberg@cs.helsinki.fi>
Cc: Eduard - Gabriel Munteanu <eduard.munteanu@linux360.ro>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: linux-mm@kvack.org <linux-mm@kvack.org>
LKML-Reference: <4B0B6EAF.80802@cn.fujitsu.com>
Signed-off-by: NIngo Molnar <mingo@elte.hu>

tools/perf/Documentation/perf-kmem.txt

+perf-kmem(1)
+==============
+
+NAME
+----
+perf-kmem - Tool to trace/measure kernel memory(slab) properties
+
+SYNOPSIS
+--------
+[verse]
+'perf kmem' {record} [<options>]
+
+DESCRIPTION
+-----------
+There's two variants of perf kmem:
+
+  'perf kmem record <command>' to record the kmem events
+  of an arbitrary workload.
+
+  'perf kmem' to report kernel memory statistics.
+
+OPTIONS
+-------
+-i <file>::
+--input=<file>::
+	Select the input file (default: perf.data)
+
+--stat=<caller|alloc>::
+	Select per callsite or per allocation statistics
+
+-s <key[,key2...]>::
+--sort=<key[,key2...]>::
+	Sort the output (default: frag,hit,bytes)
+
+-l <num>::
+--line=<num>::
+	Print n lines only
+
+--raw-ip::
+	Print raw ip instead of symbol
+
+SEE ALSO
+--------
+linkperf:perf-record[1]

tools/perf/command-list.txt

@@ -14,3 +14,4 @@ perf-timechart			mainporcelain common
 perf-top			mainporcelain common
 perf-trace			mainporcelain common
 perf-probe			mainporcelain common
+perf-kmem			mainporcelain common