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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: <Yv8umgIXfbpMFukB@kroah.com>
Date:   Fri, 19 Aug 2022 14:44:13 +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>,
        lee.schermerhorn@hp.com
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Message-Id: <A0353CE2-D014-4B35-95F1-40345D1B66E6@linux.dev>
References: <20220819052137.7985-1-songmuchun@bytedance.com>
 <Yv8umgIXfbpMFukB@kroah.com>
To:     Greg KH <gregkh@linuxfoundation.org>
Precedence: bulk


> 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?

OK. Cc Lee Schermerhorn.

>=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.

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
> 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.

I really did the test (through a VM), it works properly.

Thanks.

>=20
> thanks,
>=20
> greg k-h