linux-kernel - Re: [PATCH v9 2/4] mm: memory_hotplug: override memmap_on_memory when hugetlb_free

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Date:   Wed, 4 May 2022 11:37:43 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     Mike Kravetz <mike.kravetz@...cle.com>
Cc:     corbet@....net, akpm@...ux-foundation.org, mcgrof@...nel.org,
        keescook@...omium.org, yzaikin@...gle.com, osalvador@...e.de,
        david@...hat.com, masahiroy@...nel.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-mm@...ck.org,
        duanxiongchun@...edance.com, smuchun@...il.com
Subject: Re: [PATCH v9 2/4] mm: memory_hotplug: override memmap_on_memory
 when hugetlb_free_vmemmap=on

On Tue, May 03, 2022 at 05:23:37PM -0700, Mike Kravetz wrote:
> On 4/29/22 05:18, Muchun Song wrote:
> > When "hugetlb_free_vmemmap=on" and "memory_hotplug.memmap_on_memory"
> > are both passed to boot cmdline, the variable of "memmap_on_memory"
> > will be set to 1 even if the vmemmap pages will not be allocated from
> > the hotadded memory since the former takes precedence over the latter.
> 
> I had to read that sentence a few times before understanding what it was
> trying to say.  Not insisting, but how about this instead:
>

Sorry for my poor English.
 
> Freeing HugeTLB vmemmap pages is not compatible with allocating memmap on
> hot added memory. If "hugetlb_free_vmemmap=on" and
> memory_hotplug.memmap_on_memory" are both passed on the kernel command line,
> freeing hugetlb pages takes precedence.  However, the global variable
> memmap_on_memory will still be set to 1, even though we will not try to
> allocate memmap on hot added memory.
> 
> Not sure if that is more clear or not.
> 

Clearer than mine.

> Acked-by: Mike Kravetz <mike.kravetz@...cle.com>
>

Thanks.