From: Michal Hocko <mhocko@kernel.org>
To: "Huang, Ying" <ying.huang@intel.com>
Cc: "Andrew Morton" <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org,
"Zi Yan" <ziy@nvidia.com>,
"Andrea Arcangeli" <aarcange@redhat.com>,
"Kirill A . Shutemov" <kirill.shutemov@linux.intel.com>,
"Vlastimil Babka" <vbabka@suse.cz>,
"Alexey Dobriyan" <adobriyan@gmail.com>,
"Konstantin Khlebnikov" <khlebnikov@yandex-team.ru>,
"J�r�me Glisse" <jglisse@redhat.com>,
"Yang Shi" <yang.shi@linux.alibaba.com>
Subject: Re: [PATCH -V2] /proc/PID/smaps: Add PMD migration entry parsing
Date: Thu, 2 Apr 2020 10:21:42 +0200 [thread overview]
Message-ID: <20200402082142.GL22681@dhcp22.suse.cz> (raw)
In-Reply-To: <87v9mifgui.fsf@yhuang-dev.intel.com>
On Thu 02-04-20 16:10:29, Huang, Ying wrote:
> Michal Hocko <mhocko@kernel.org> writes:
>
> > On Thu 02-04-20 15:03:23, Huang, Ying wrote:
[...]
> >> > Could you explain why do we need this WARN_ON? I haven't really checked
> >> > the swap support for THP but cannot we have normal swap pmd entries?
> >>
> >> I have some patches to add the swap pmd entry support, but they haven't
> >> been merged yet.
> >>
> >> Similar checks are for all THP migration code paths, so I follow the
> >> same style.
> >
> > I haven't checked other migration code paths but what is the reason to
> > add the warning here? Even if this shouldn't happen, smaps is perfectly
> > fine to ignore that situation, no?
>
> Yes. smaps itself is perfectly fine to ignore it. I think this is used
> to find bugs in other code paths such as THP migration related.
Please do not add new warnings without a good an strong reasons. As a
matter of fact there are people running with panic_on_warn and each
warning is fatal for them. Please also note that this is a user trigable
path and that requires even more care.
--
Michal Hocko
SUSE Labs
next prev parent reply other threads:[~2020-04-02 8:21 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-04-02 2:00 [PATCH -V2] /proc/PID/smaps: Add PMD migration entry parsing Huang, Ying
2020-04-02 6:44 ` Michal Hocko
2020-04-02 7:03 ` Huang, Ying
2020-04-02 7:44 ` Michal Hocko
2020-04-02 8:10 ` Huang, Ying
2020-04-02 8:21 ` Michal Hocko [this message]
2020-04-02 8:27 ` Huang, Ying
2020-04-02 8:29 ` Konstantin Khlebnikov
2020-04-02 8:58 ` Michal Hocko
2020-04-02 15:52 ` Yang Shi
2020-04-02 12:53 ` Kirill A. Shutemov
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