linux-kernel - Re: [PATCH] mm: hugetlb: simplify per-node sysfs creation and removal

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Date:   Fri, 19 Aug 2022 09:00:05 +0200
From:   Greg KH <gregkh@...uxfoundation.org>
To:     Muchun Song <muchun.song@...ux.dev>
Cc:     Muchun Song <songmuchun@...edance.com>, rafael@...nel.org,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Oscar Salvador <osalvador@...e.de>,
        David Hildenbrand <david@...hat.com>,
        linux-kernel@...r.kernel.org, Linux MM <linux-mm@...ck.org>,
        lee.schermerhorn@...com
Subject: Re: [PATCH] mm: hugetlb: simplify per-node sysfs creation and removal

On Fri, Aug 19, 2022 at 02:44:13PM +0800, Muchun Song wrote:
> 
> 
> > On Aug 19, 2022, at 14:32, Greg KH <gregkh@...uxfoundation.org> wrote:
> > 
> > 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.
> >> 
> >>  39da08cb074c ("hugetlb: offload per node attribute registrations")
> > 
> > Any specific reason why you did not cc: the original author of this
> > commit, or anyone else on the patch?
> 
> OK. Cc Lee Schermerhorn.

He can't see the patch here, so there is no context.  Please resend the
whole thing.  You also didn't copy the people who signed off on it (i.e.
Andi), any reason why?

> >> 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.
> > 
> > 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).
> 
> > 
> > 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.

How about on real hardware?  On a HUGE system with real hardware?  On a
small system?

thanks,

greg k-h