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Subject: Re: [PATCH] mm: hugetlb: simplify per-node sysfs creation and removal
From:   Muchun Song <muchun.song@linux.dev>
In-Reply-To: <A0353CE2-D014-4B35-95F1-40345D1B66E6@linux.dev>
Date:   Fri, 19 Aug 2022 14:56:56 +0800
Cc:     Muchun Song <songmuchun@bytedance.com>, rafael@kernel.org,
        Mike Kravetz <mike.kravetz@oracle.com>,
        Andrew Morton <akpm@linux-foundation.org>,
        Oscar Salvador <osalvador@suse.de>,
        David Hildenbrand <david@redhat.com>,
        linux-kernel@vger.kernel.org, Linux MM <linux-mm@kvack.org>
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Message-Id: <0F3FE8B0-9ADB-423D-A2FE-2AF1A3A6E619@linux.dev>
References: <20220819052137.7985-1-songmuchun@bytedance.com>
 <Yv8umgIXfbpMFukB@kroah.com> <A0353CE2-D014-4B35-95F1-40345D1B66E6@linux.dev>
To:     Greg KH <gregkh@linuxfoundation.org>
Precedence: bulk


> On Aug 19, 2022, at 14:44, Muchun Song <muchun.song@linux.dev> wrote:
>=20
>=20
>=20
>> On Aug 19, 2022, at 14:32, Greg KH <gregkh@linuxfoundation.org> =
wrote:
>>=20
>> On Fri, Aug 19, 2022 at 01:21:37PM +0800, Muchun Song wrote:
>>> The following commit offload per-node sysfs creation and removal to =
a kworker and
>>> did not say why it is needed.  And it also said "I don't know that =
this is
>>> absolutely required".  It seems like the author was not sure as =
well.  Since it
>>> only complicates the code, this patch will revert the changes to =
simplify the code.
>>>=20
>>> 39da08cb074c ("hugetlb: offload per node attribute registrations")
>>=20
>> Any specific reason why you did not cc: the original author of this
>> commit, or anyone else on the patch?
>=20
> OK. Cc Lee Schermerhorn.

Unluckily, I guess the email address is out of date since I just got =
bounced mail
(Undelivered Mail Returned to Sender). Remove lee.schermerhorn@hp.com =
from the
Cc list.

>=20
>>=20
>>> We could use memory hotplug notifier to do per-node sysfs creation =
and removal
>>> instead of inserting those operations to node registration and =
unregistration.
>>> Then, it can reduce the code coupling between node.c and hugetlb.c.  =
Also, it can
>>> simplify the code.
>>=20
>> I do not think we had memory hotplug notifier back in 2009 when this
>> commit was first written.
>=20
> Maybe not. Commit 39da08cb074c is merger in 2009. However, hotplug =
notifier mechanism
> is merged in 2006. The document is updated in 2007 (see commit =
10020ca246c5).
>=20
>>=20
>> How did you test this?  Did you use a HUGETLBFS system and verify =
that
>> everything still works properly?  You are deleting a lot of code =
(always
>> nice), but making sure everything is still operating the same is a =
good
>> thing.
>=20
> I really did the test (through a VM), it works properly.
>=20
> Thanks.
>=20
>>=20
>> thanks,
>>=20
>> greg k-h