tools/vm/page_owner_sort.c: support sorting blocks by multiple keys

When viewing page owner information, we may want to sort blocks of
information by multiple keys, since one single key does not uniquely
identify a block. Therefore, following adjustments are made:

1. Add a new --sort option to support sorting blocks of information by
multiple keys.

	./page_owner_sort <input> <output> --sort=<order>
	./page_owner_sort <input> <output> --sort <order>

<order> is a single argument in the form of a comma-separated list,
which offers a way to specify sorting order.

Sorting syntax is [+|-]key[,[+|-]key[,...]]. The ascending or descending
order can be specified by adding the + (ascending, default) or - (descend
-ing) prefix to the key:

	./page_owner_sort <input> <output> [option] --sort -key1,+key2,key3...

For example, to sort the blocks first by task command name in lexicographic
order and then by pid in ascending numerical order, use the following:

	./page_owner_sort <input> <output> --sort=name,+pid

To sort the blocks first by pid in ascending order and then by timestamp
of the page when it is allocated in descending order, use the following:

	./page_owner_sort <input> <output> --sort=pid,-alloc_ts

2. Add explanations of a newly added --sort option in the function usage()
and the document(Documentation/vm/page_owner.rst).

This work is coauthored by
	Yixuan Cao
	Shenghong Han
	Yinan Zhang
	Chongxi Zhao
	Yuhong Feng
	Yongqiang Liu

Link: https://lkml.kernel.org/r/20220401024856.767-3-yejiajian2018@email.szu.edu.cn
Signed-off-by: Jiajian Ye <yejiajian2018@email.szu.edu.cn>
Cc: Chongxi Zhao <zhaochongxi2019@email.szu.edu.cn>
Cc: Shenghong Han <hanshenghong2019@email.szu.edu.cn>
Cc: Yinan Zhang <zhangyinan2019@email.szu.edu.cn>
Cc: Yixuan Cao <caoyixuan2019@email.szu.edu.cn>
Cc: Yongqiang Liu <liuyongqiang13@huawei.com>
Cc: Yuhong Feng <yuhongf@szu.edu.cn>
Cc: Haowen Bai <baihaowen@meizu.com>
Cc: Sean Anderson <seanga2@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

1 files changed, 23 insertions, 1 deletions

diff --git a/Documentation/vm/page_owner.rst b/Documentation/vm/page_owner.rst
index 3102f91d635c..523bf3419512 100644
--- a/Documentation/vm/page_owner.rst
+++ b/Documentation/vm/page_owner.rst
@@ -121,6 +121,14 @@ Usage
 		-r		Sort by memory release time.
 		-s		Sort by stack trace.
 		-t		Sort by times (default).
+		--sort <order>	Specify sorting order.  Sorting syntax is [+|-]key[,[+|-]key[,...]].
+				Choose a key from the **STANDARD FORMAT SPECIFIERS** section. The "+" is
+				optional since default direction is increasing numerical or lexicographic
+				order. Mixed use of abbreviated and complete-form of keys is allowed.
+
+		Examples:
+				./page_owner_sort <input> <output> --sort=n,+pid,-tgid
+				./page_owner_sort <input> <output> --sort=at
 
    additional function::
 
@@ -165,9 +173,23 @@ STANDARD FORMAT SPECIFIERS
 ==========================
 ::
 
+For --sort option:
+
+	KEY		LONG		DESCRIPTION
+	p		pid		process ID
+	tg		tgid		thread group ID
+	n		name		task command name
+	st		stacktrace	stack trace of the page allocation
+	T		txt		full text of block
+	ft		free_ts		timestamp of the page when it was released
+	at		alloc_ts	timestamp of the page when it was allocated
+
+For --curl option:
+
 	KEY		LONG		DESCRIPTION
 	p		pid		process ID
 	tg		tgid		thread group ID
 	n		name		task command name
 	f		free		whether the page has been released or not
-	st		stacktrace	stace trace of the page allocation
+	st		stacktrace	stack trace of the page allocation
+