[v2,0/4] debug_pagealloc improvements through page_owner

Message

Vlastimil Babka Aug. 20, 2019, 1:18 p.m. UTC

v2: also fix THP split handling (added Patch 1) per Kirill

The debug_pagealloc functionality serves a similar purpose on the page
allocator level that slub_debug does on the kmalloc level, which is to detect
bad users. One notable feature that slub_debug has is storing stack traces of
who last allocated and freed the object. On page level we track allocations via
page_owner, but that info is discarded when freeing, and we don't track freeing
at all. This series improves those aspects. With both debug_pagealloc and
page_owner enabled, we can then get bug reports such as the example in Patch 4.

SLUB debug tracking additionaly stores cpu, pid and timestamp. This could be
added later, if deemed useful enough to justify the additional page_ext
structure size.

Vlastimil Babka (4):
  mm, page_owner: handle THP splits correctly
  mm, page_owner: record page owner for each subpage
  mm, page_owner: keep owner info when freeing the page
  mm, page_owner, debug_pagealloc: save and dump freeing stack trace

 .../admin-guide/kernel-parameters.txt         |   2 +
 include/linux/page_ext.h                      |   1 +
 mm/Kconfig.debug                              |   4 +-
 mm/huge_memory.c                              |   4 +
 mm/page_owner.c                               | 123 +++++++++++++-----
 5 files changed, 100 insertions(+), 34 deletions(-)

Comments

Andrew Morton Aug. 22, 2019, 11:03 p.m. UTC | #1

On Tue, 20 Aug 2019 15:18:24 +0200 Vlastimil Babka <[e-mail]> wrote:

> v2: also fix THP split handling (added Patch 1) per Kirill
> 
> The debug_pagealloc functionality serves a similar purpose on the page
> allocator level that slub_debug does on the kmalloc level, which is to detect
> bad users. One notable feature that slub_debug has is storing stack traces of
> who last allocated and freed the object. On page level we track allocations via
> page_owner, but that info is discarded when freeing, and we don't track freeing
> at all. This series improves those aspects. With both debug_pagealloc and
> page_owner enabled, we can then get bug reports such as the example in Patch 4.
> 
> SLUB debug tracking additionaly stores cpu, pid and timestamp. This could be
> added later, if deemed useful enough to justify the additional page_ext
> structure size.

Thanks.  I split [1/1] out of the series as a bugfix and turned this
into a three-patch series.

Andrew Morton Sept. 20, 2019, 11:34 p.m. UTC | #2

On Thu, 22 Aug 2019 16:03:44 -0700 Andrew Morton <[e-mail]> wrote:

> On Tue, 20 Aug 2019 15:18:24 +0200 Vlastimil Babka <[e-mail]> wrote:
> 
> > v2: also fix THP split handling (added Patch 1) per Kirill
> > 
> > The debug_pagealloc functionality serves a similar purpose on the page
> > allocator level that slub_debug does on the kmalloc level, which is to detect
> > bad users. One notable feature that slub_debug has is storing stack traces of
> > who last allocated and freed the object. On page level we track allocations via
> > page_owner, but that info is discarded when freeing, and we don't track freeing
> > at all. This series improves those aspects. With both debug_pagealloc and
> > page_owner enabled, we can then get bug reports such as the example in Patch 4.
> > 
> > SLUB debug tracking additionaly stores cpu, pid and timestamp. This could be
> > added later, if deemed useful enough to justify the additional page_ext
> > structure size.
> 
> Thanks.  I split [1/1] out of the series as a bugfix and turned this
> into a three-patch series.
> 

None of which anyone has yet reviewed :(