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Sender: Minchan Kim <minchan.kim@gmail.com>
Date:   Wed, 10 Mar 2021 08:05:36 -0800
From:   Minchan Kim <minchan@kernel.org>
To:     Michal Hocko <mhocko@suse.com>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        linux-mm <linux-mm@kvack.org>,
        LKML <linux-kernel@vger.kernel.org>,
        John Dias <joaodias@google.com>,
        David Hildenbrand <david@redhat.com>,
        Jason Baron <jbaron@akamai.com>
Subject: Re: [PATCH v2] mm: page_alloc: dump migrate-failed pages
Message-ID: <YEjuUHBDKu2uX4EO@google.com>
References: <20210308202047.1903802-1-minchan@kernel.org>
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 <YEefLYiX6rF3Uk4E@google.com>
 <YEh4doXvyuRl5BDB@google.com>
 <YEjEefQpBHV5eBXj@dhcp22.suse.cz>
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On Wed, Mar 10, 2021 at 02:07:05PM +0100, Michal Hocko wrote:
> On Tue 09-03-21 23:42:46, Minchan Kim wrote:
> > 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(-)
> 
> The is a lot of churn indeed. Have you considered adding $FOO_lglvl
> variants for those so that you can use them for your particular case
> without affecting most of existing users? Something similar we have
> discussed in other email thread regarding lru_add_drain_all?

I thought that way but didn't try since it couldn't make them
atomic(For example, other printk place in other context will
affect by the $FOO_lglvl).