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Date:   Tue, 19 Sep 2023 14:32:25 -0700
From:   Mike Kravetz <mike.kravetz@oracle.com>
To:     Muchun Song <muchun.song@linux.dev>
Cc:     linux-mm@kvack.org, linux-kernel@vger.kernel.org,
        Muchun Song <songmuchun@bytedance.com>,
        Joao Martins <joao.m.martins@oracle.com>,
        Oscar Salvador <osalvador@suse.de>,
        David Hildenbrand <david@redhat.com>,
        Miaohe Lin <linmiaohe@huawei.com>,
        David Rientjes <rientjes@google.com>,
        Anshuman Khandual <anshuman.khandual@arm.com>,
        Naoya Horiguchi <naoya.horiguchi@linux.dev>,
        Barry Song <21cnbao@gmail.com>, Michal Hocko <mhocko@suse.com>,
        Matthew Wilcox <willy@infradead.org>,
        Xiongchun Duan <duanxiongchun@bytedance.com>,
        Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [PATCH v4 5/8] hugetlb: batch freeing of vmemmap pages
Message-ID: <20230919213225.GC425719@monkey>
References: <20230918230202.254631-1-mike.kravetz@oracle.com>
 <20230918230202.254631-6-mike.kravetz@oracle.com>
 <9a716de0-91c3-5f29-4f88-391b9aaeb5ce@linux.dev>
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On 09/19/23 14:09, Muchun Song wrote:
> 
> 
> On 2023/9/19 07:01, Mike Kravetz wrote:
> > Now that batching of hugetlb vmemmap optimization processing is possible,
> > batch the freeing of vmemmap pages.  When freeing vmemmap pages for a
> > hugetlb page, we add them to a list that is freed after the entire batch
> > has been processed.
> > 
> > This enhances the ability to return contiguous ranges of memory to the
> > low level allocators.
> > 
> > Signed-off-by: Mike Kravetz <mike.kravetz@oracle.com>
> 
> Reviewed-by: Muchun Song <songmuchun@bytedance.com>
> 
> One nit bellow.
> 
> > ---
> >   mm/hugetlb_vmemmap.c | 85 ++++++++++++++++++++++++++++++--------------
> >   1 file changed, 59 insertions(+), 26 deletions(-)
> > 
> > diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c
> > index 463a4037ec6e..147ed15bcae4 100644
> > --- a/mm/hugetlb_vmemmap.c
> > +++ b/mm/hugetlb_vmemmap.c
> > @@ -222,6 +222,9 @@ static void free_vmemmap_page_list(struct list_head *list)
> >   {
> >   	struct page *page, *next;
> > +	if (list_empty(list))
> > +		return;
> 
> It seems unnecessary since the following "list_for_each_entry_safe"
> could handle empty-list case. Right?
> 

Yes, it is an over-optimization that is not really necessary.
I will remove it.

-- 
Mike Kravetz