linux-kernel - Re: [PATCH v2] mm: page_alloc: dump migrate-failed pages

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Message-ID: <YEh4doXvyuRl5BDB@google.com>
Date:   Tue, 9 Mar 2021 23:42:46 -0800
From:   Minchan Kim <minchan@...nel.org>
To:     Michal Hocko <mhocko@...e.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        linux-mm <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        John Dias <joaodias@...gle.com>,
        David Hildenbrand <david@...hat.com>,
        Jason Baron <jbaron@...mai.com>
Subject: Re: [PATCH v2] mm: page_alloc: dump migrate-failed pages

On Tue, Mar 09, 2021 at 08:15:41AM -0800, Minchan Kim wrote:

< snip >

> > [...]
> > > +void dump_migrate_failure_pages(struct list_head *page_list)
> > > +{
> > > +	DEFINE_DYNAMIC_DEBUG_METADATA(descriptor,
> > > +			"migrate failure");
> > > +	if (DYNAMIC_DEBUG_BRANCH(descriptor) &&
> > > +			alloc_contig_ratelimit()) {
> > > +		struct page *page;
> > > +
> > > +		WARN(1, "failed callstack");
> > > +		list_for_each_entry(page, page_list, lru)
> > > +			dump_page(page, "migration failure");
> > > +	}
> > 
> > Apart from the above, do we have to warn for something that is a
> > debugging aid? A similar concern wrt dump_page which uses pr_warn and
> 
> Make sense.
> 
> > page owner is using even pr_alert.
> > Would it make sense to add a loglevel parameter both into __dump_page
> > and dump_page_owner?
> 
> Let me try it.

I looked though them and made first draft to clean them up.

It's bigger than my initial expectaion because there are many callsites
to use dump_page and stack_trace_print inconsistent loglevel. 
Since it's not a specific problem for this work, I'd like to deal with
it as separate patchset since I don't want to be stuck on here for my
initial goal.

FYI,

Subject: [RFC 0/5] make dump_page aware of loglevel

- Forked from [1]

dump_page uses __dump_page and dump_page_owner internally to
print various information. However, their printk loglevel are
inconsistent in that

__dump_page: KERN_WARNING
__dump_page_owner: KERN_ALERT
        stack_trace_print: KERN_DEFAULT

To make them consistent from dump_page, this patch introduces
pr_loglevel in printk and make the utility functions aware of
loglevel. Finally, last patch changes dump_page to support
loglevel to make the printing level consistent.

[1] https://lore.kernel.org/linux-mm/YEdAw6gnp9XxoWUQ@dhcp22.suse.cz/

Minchan Kim (5):
  mm: introduce pr_loglevel for __dump_[page]_owner
  stacktrace: stack_trace_print aware of loglevel
  mm: page_owner: dump_page_owner aware of loglevel
  mm: debug: __dump_page aware of loglevel
  mm: debug: dump_page aware of loglevel
  drivers/md/dm-bufio.c       |  2 +-
 drivers/virtio/virtio_mem.c |  2 +-
 fs/btrfs/ref-verify.c       |  2 +-
 fs/fuse/dev.c               |  2 +-
 include/linux/mmdebug.h     | 10 ++++++----
 include/linux/page_owner.h  |  8 ++++----
 include/linux/printk.h      | 12 +++++++++++
 include/linux/stacktrace.h  |  4 ++--
 kernel/backtracetest.c      |  2 +-
 kernel/dma/debug.c          |  3 ++-
 kernel/kcsan/report.c       |  7 ++++---
 kernel/locking/lockdep.c    |  3 ++-
 kernel/stacktrace.c         |  5 +++--
 mm/debug.c                  | 40 ++++++++++++++++++-------------------
 mm/filemap.c                |  2 +-
 mm/gup_test.c               |  4 ++--
 mm/huge_memory.c            |  4 ++--
 mm/kasan/report.c           |  4 ++--
 mm/kfence/report.c          |  3 ++-
 mm/kmemleak.c               |  2 +-
 mm/memory.c                 |  2 +-
 mm/memory_hotplug.c         |  4 ++--
 mm/page_alloc.c             |  4 ++--
 mm/page_isolation.c         |  2 +-
 mm/page_owner.c             | 24 +++++++++++-----------
 25 files changed, 88 insertions(+), 69 deletions(-)