From: Michal Hocko <mhocko@suse.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: Minchan Kim <minchan@kernel.org>,
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
Date: Wed, 10 Mar 2021 14:54:57 +0100 [thread overview]
Message-ID: <YEjPsfAApvVmO4Jb@dhcp22.suse.cz> (raw)
In-Reply-To: <20210310132623.GO3479805@casper.infradead.org>
On Wed 10-03-21 13:26:23, Matthew Wilcox wrote:
> On Tue, Mar 09, 2021 at 10:32:51AM +0100, Michal Hocko wrote:
> > 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
> > page owner is using even pr_alert.
> > Would it make sense to add a loglevel parameter both into __dump_page
> > and dump_page_owner?
>
> No. What would make sense is turning __dump_page() inside-out.
> Something like printk("%pP\n");
>
> In lib/vsprintf.c, there's a big switch statement in the function
> pointer() that handles printing things like IPv6 addresses, dentries,
> and function symbols.
>
> Then we can do whatever we want around the new %pP, including choosing
> the log level, adding additional information, choosing to dump the page
> to a sysfs file, etc, etc.
Hmm, __dump_page has grown quite some heavy lifting over time and I am
not sure this is a good candidate to put into printk proper (e.g. is it
safe/reasonable to call get_kernel_nofault from printk - aka arbitrary
context)?.
But you've got a point that such a printk format wouldn't need to be 1:1
with the existing __dump_page. There is quite a lot to infer from page
count, map count, flags, page type already. Then a question would be
what is an actual advantage of %pP over dump_page_info(loglvl, p). One I
can see is that %pP would allow to dump the state into a string and so
it would be more versatile but I am not aware of a usecase for that
(maybe tracing?).
--
Michal Hocko
SUSE Labs
prev parent reply other threads:[~2021-03-10 13:55 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-08 20:20 [PATCH v2] mm: page_alloc: dump migrate-failed pages Minchan Kim
2021-03-08 21:29 ` kernel test robot
2021-03-08 22:29 ` Minchan Kim
2021-03-09 0:41 ` [kbuild-all] " Rong Chen
2021-03-09 2:23 ` Minchan Kim
2021-03-09 0:21 ` Andrew Morton
2021-03-09 2:21 ` Minchan Kim
2021-03-09 0:30 ` kernel test robot
2021-03-09 0:30 ` [RFC PATCH] mm: page_alloc: alloc_contig_ratelimit() can be static kernel test robot
2021-03-09 9:32 ` [PATCH v2] mm: page_alloc: dump migrate-failed pages Michal Hocko
2021-03-09 16:15 ` Minchan Kim
2021-03-09 16:32 ` Michal Hocko
2021-03-09 17:27 ` Minchan Kim
2021-03-10 13:04 ` Michal Hocko
2021-03-10 15:59 ` Minchan Kim
2021-03-10 7:42 ` Minchan Kim
2021-03-10 8:20 ` David Hildenbrand
2021-03-10 15:45 ` Minchan Kim
2021-03-10 13:07 ` Michal Hocko
2021-03-10 16:05 ` Minchan Kim
2021-03-10 16:46 ` Michal Hocko
2021-03-10 17:06 ` Minchan Kim
2021-03-10 18:07 ` Minchan Kim
2021-03-10 13:26 ` Matthew Wilcox
2021-03-10 13:54 ` Michal Hocko [this message]
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