linux-kernel - Re: [PATCH v4 5/8] hugetlb: batch freeing of vmemmap pages

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Message-ID: <20230919213225.GC425719@monkey>
Date:   Tue, 19 Sep 2023 14:32:25 -0700
From:   Mike Kravetz <mike.kravetz@...cle.com>
To:     Muchun Song <muchun.song@...ux.dev>
Cc:     linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        Muchun Song <songmuchun@...edance.com>,
        Joao Martins <joao.m.martins@...cle.com>,
        Oscar Salvador <osalvador@...e.de>,
        David Hildenbrand <david@...hat.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        David Rientjes <rientjes@...gle.com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Naoya Horiguchi <naoya.horiguchi@...ux.dev>,
        Barry Song <21cnbao@...il.com>, Michal Hocko <mhocko@...e.com>,
        Matthew Wilcox <willy@...radead.org>,
        Xiongchun Duan <duanxiongchun@...edance.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v4 5/8] hugetlb: batch freeing of vmemmap pages

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@...cle.com>
> 
> Reviewed-by: Muchun Song <songmuchun@...edance.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