Adding upstream version 6.1.76.upstream/6.1.76

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 189 insertions, 0 deletions

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+.. _page_owner:
+
+==================================================
+page owner: Tracking about who allocated each page
+==================================================
+
+Introduction
+============
+
+page owner is for the tracking about who allocated each page.
+It can be used to debug memory leak or to find a memory hogger.
+When allocation happens, information about allocation such as call stack
+and order of pages is stored into certain storage for each page.
+When we need to know about status of all pages, we can get and analyze
+this information.
+
+Although we already have tracepoint for tracing page allocation/free,
+using it for analyzing who allocate each page is rather complex. We need
+to enlarge the trace buffer for preventing overlapping until userspace
+program launched. And, launched program continually dump out the trace
+buffer for later analysis and it would change system behaviour with more
+possibility rather than just keeping it in memory, so bad for debugging.
+
+page owner can also be used for various purposes. For example, accurate
+fragmentation statistics can be obtained through gfp flag information of
+each page. It is already implemented and activated if page owner is
+enabled. Other usages are more than welcome.
+
+page owner is disabled by default. So, if you'd like to use it, you need
+to add "page_owner=on" to your boot cmdline. If the kernel is built
+with page owner and page owner is disabled in runtime due to not enabling
+boot option, runtime overhead is marginal. If disabled in runtime, it
+doesn't require memory to store owner information, so there is no runtime
+memory overhead. And, page owner inserts just two unlikely branches into
+the page allocator hotpath and if not enabled, then allocation is done
+like as the kernel without page owner. These two unlikely branches should
+not affect to allocation performance, especially if the static keys jump
+label patching functionality is available. Following is the kernel's code
+size change due to this facility.
+
+Although enabling page owner increases kernel size by several kilobytes,
+most of this code is outside page allocator and its hot path. Building
+the kernel with page owner and turning it on if needed would be great
+option to debug kernel memory problem.
+
+There is one notice that is caused by implementation detail. page owner
+stores information into the memory from struct page extension. This memory
+is initialized some time later than that page allocator starts in sparse
+memory system, so, until initialization, many pages can be allocated and
+they would have no owner information. To fix it up, these early allocated
+pages are investigated and marked as allocated in initialization phase.
+Although it doesn't mean that they have the right owner information,
+at least, we can tell whether the page is allocated or not,
+more accurately. On 2GB memory x86-64 VM box, 13343 early allocated pages
+are catched and marked, although they are mostly allocated from struct
+page extension feature. Anyway, after that, no page is left in
+un-tracking state.
+
+Usage
+=====
+
+1) Build user-space helper::
+
+	cd tools/vm
+	make page_owner_sort
+
+2) Enable page owner: add "page_owner=on" to boot cmdline.
+
+3) Do the job that you want to debug.
+
+4) Analyze information from page owner::
+
+	cat /sys/kernel/debug/page_owner > page_owner_full.txt
+	./page_owner_sort page_owner_full.txt sorted_page_owner.txt
+
+   The general output of ``page_owner_full.txt`` is as follows::
+
+	Page allocated via order XXX, ...
+	PFN XXX ...
+	// Detailed stack
+
+	Page allocated via order XXX, ...
+	PFN XXX ...
+	// Detailed stack
+    By default, it will do full pfn dump, to start with a given pfn,
+    page_owner supports fseek.
+
+    FILE *fp = fopen("/sys/kernel/debug/page_owner", "r");
+    fseek(fp, pfn_start, SEEK_SET);
+
+   The ``page_owner_sort`` tool ignores ``PFN`` rows, puts the remaining rows
+   in buf, uses regexp to extract the page order value, counts the times
+   and pages of buf, and finally sorts them according to the parameter(s).
+
+   See the result about who allocated each page
+   in the ``sorted_page_owner.txt``. General output::
+
+	XXX times, XXX pages:
+	Page allocated via order XXX, ...
+	// Detailed stack
+
+   By default, ``page_owner_sort`` is sorted according to the times of buf.
+   If you want to sort by the page nums of buf, use the ``-m`` parameter.
+   The detailed parameters are:
+
+   fundamental function::
+
+	Sort:
+		-a		Sort by memory allocation time.
+		-m		Sort by total memory.
+		-p		Sort by pid.
+		-P		Sort by tgid.
+		-n		Sort by task command name.
+		-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::
+
+	Cull:
+		--cull <rules>
+				Specify culling rules.Culling syntax is key[,key[,...]].Choose a
+				multi-letter key from the **STANDARD FORMAT SPECIFIERS** section.
+
+		<rules> is a single argument in the form of a comma-separated list,
+		which offers a way to specify individual culling rules.  The recognized
+		keywords are described in the **STANDARD FORMAT SPECIFIERS** section below.
+		<rules> can be specified by the sequence of keys k1,k2, ..., as described in
+		the STANDARD SORT KEYS section below. Mixed use of abbreviated and
+		complete-form of keys is allowed.
+
+		Examples:
+				./page_owner_sort <input> <output> --cull=stacktrace
+				./page_owner_sort <input> <output> --cull=st,pid,name
+				./page_owner_sort <input> <output> --cull=n,f
+
+	Filter:
+		-f		Filter out the information of blocks whose memory has been released.
+
+	Select:
+		--pid <pidlist>		Select by pid. This selects the blocks whose process ID
+					numbers appear in <pidlist>.
+		--tgid <tgidlist>	Select by tgid. This selects the blocks whose thread
+					group ID numbers appear in <tgidlist>.
+		--name <cmdlist>	Select by task command name. This selects the blocks whose
+					task command name appear in <cmdlist>.
+
+		<pidlist>, <tgidlist>, <cmdlist> are single arguments in the form of a comma-separated list,
+		which offers a way to specify individual selecting rules.
+
+
+		Examples:
+				./page_owner_sort <input> <output> --pid=1
+				./page_owner_sort <input> <output> --tgid=1,2,3
+				./page_owner_sort <input> <output> --name name1,name2
+
+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
+	ator		allocator	memory allocator for pages
+
+  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	stack trace of the page allocation
+	ator		allocator	memory allocator for pages