The patch titled
Subject: mm,page_owner: update Documentation regarding page_owner_stacks
has been added to the -mm mm-unstable branch. Its filename is
mmpage_owner-update-documentation-regarding-page_owner_stacks.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mmpage_owner-update-documentation-regarding-page_owner_stacks.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Oscar Salvador <osalvador@xxxxxxx>
Subject: mm,page_owner: update Documentation regarding page_owner_stacks
Date: Wed, 14 Feb 2024 18:01:57 +0100
Update page_owner documentation including the new page_owner_stacks
feature to show how it can be used.
Link: https://lkml.kernel.org/r/20240214170157.17530-8-osalvador@xxxxxxx
Signed-off-by: Oscar Salvador <osalvador@xxxxxxx>
Cc: Alexander Potapenko <glider@xxxxxxxxxx>
Cc: Andrey Konovalov <andreyknvl@xxxxxxxxx>
Cc: Marco Elver <elver@xxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Vlastimil Babka <vbabka@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/mm/page_owner.rst | 45 ++++++++++++++++++++++++++++++
1 file changed, 45 insertions(+)
--- a/Documentation/mm/page_owner.rst~mmpage_owner-update-documentation-regarding-page_owner_stacks
+++ a/Documentation/mm/page_owner.rst
@@ -24,6 +24,11 @@ fragmentation statistics can be obtained
each page. It is already implemented and activated if page owner is
enabled. Other usages are more than welcome.
+It can also be used to show all the stacks and their outstanding
+allocations, which gives us a quick overview of where the memory is going
+without the need to screen through all the pages and match the allocation
+and free operation.
+
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
@@ -68,6 +73,46 @@ Usage
4) Analyze information from page owner::
+ cat /sys/kernel/debug/page_owner_stacks/show_stacks > stacks.txt
+ cat stacks.txt
+ prep_new_page+0xa9/0x120
+ get_page_from_freelist+0x7e6/0x2140
+ __alloc_pages+0x18a/0x370
+ new_slab+0xc8/0x580
+ ___slab_alloc+0x1f2/0xaf0
+ __slab_alloc.isra.86+0x22/0x40
+ kmem_cache_alloc+0x31b/0x350
+ __khugepaged_enter+0x39/0x100
+ dup_mmap+0x1c7/0x5ce
+ copy_process+0x1afe/0x1c90
+ kernel_clone+0x9a/0x3c0
+ __do_sys_clone+0x66/0x90
+ do_syscall_64+0x7f/0x160
+ entry_SYSCALL_64_after_hwframe+0x6c/0x74
+ stack_count: 234
+ ...
+ ...
+ echo 7000 > /sys/kernel/debug/page_owner_stacks/count_threshold
+ cat /sys/kernel/debug/page_owner_stacks/show_stacks> stacks_7000.txt
+ cat stacks_7000.txt
+ prep_new_page+0xa9/0x120
+ get_page_from_freelist+0x7e6/0x2140
+ __alloc_pages+0x18a/0x370
+ alloc_pages_mpol+0xdf/0x1e0
+ folio_alloc+0x14/0x50
+ filemap_alloc_folio+0xb0/0x100
+ page_cache_ra_unbounded+0x97/0x180
+ filemap_fault+0x4b4/0x1200
+ __do_fault+0x2d/0x110
+ do_pte_missing+0x4b0/0xa30
+ __handle_mm_fault+0x7fa/0xb70
+ handle_mm_fault+0x125/0x300
+ do_user_addr_fault+0x3c9/0x840
+ exc_page_fault+0x68/0x150
+ asm_exc_page_fault+0x22/0x30
+ stack_count: 8248
+ ...
+
cat /sys/kernel/debug/page_owner > page_owner_full.txt
./page_owner_sort page_owner_full.txt sorted_page_owner.txt
_
Patches currently in -mm which might be from osalvador@xxxxxxx are
lib-stackdepot-fix-first-entry-having-a-0-handle.patch
lib-stackdepot-move-stack_record-struct-definition-into-the-header.patch
mmpage_owner-maintain-own-list-of-stack_records-structs.patch
mmpage_owner-implement-the-tracking-of-the-stacks-count.patch
mmpage_owner-display-all-stacks-and-their-count.patch
mmpage_owner-filter-out-stacks-by-a-threshold.patch
mmpage_owner-update-documentation-regarding-page_owner_stacks.patch
