linux-kernel - Re: [PATCH v2 2/2] hugetlb: optimize update_and_free_pages

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Message-Id: <CCCD27BE-0127-4148-92A8-673075A976E0@linux.dev>
Date:   Wed, 19 Jul 2023 11:35:44 +0800
From:   Muchun Song <muchun.song@...ux.dev>
To:     Mike Kravetz <mike.kravetz@...cle.com>
Cc:     Linux Memory Management List <linux-mm@...ck.org>,
        LKML <linux-kernel@...r.kernel.org>,
        Jiaqi Yan <jiaqiyan@...gle.com>,
        Naoya Horiguchi <naoya.horiguchi@...ux.dev>,
        Muchun Song <songmuchun@...edance.com>,
        Miaohe Lin <linmiaohe@...wei.com>,
        Axel Rasmussen <axelrasmussen@...gle.com>,
        James Houghton <jthoughton@...gle.com>,
        Michal Hocko <mhocko@...e.com>,
        Andrew Morton <akpm@...ux-foundation.org>
Subject: Re: [PATCH v2 2/2] hugetlb: optimize update_and_free_pages_bulk to
 avoid lock cycles



> On Jul 18, 2023, at 08:49, Mike Kravetz <mike.kravetz@...cle.com> wrote:
> 
> update_and_free_pages_bulk is designed to free a list of hugetlb pages
> back to their associated lower level allocators.  This may require
> allocating vmemmmap pages associated with each hugetlb page.  The
> hugetlb page destructor must be changed before pages are freed to lower
> level allocators.  However, the destructor must be changed under the
> hugetlb lock.  This means there is potentially one lock cycle per page.
> 
> Minimize the number of lock cycles in update_and_free_pages_bulk by:
> 1) allocating necessary vmemmap for all hugetlb pages on the list
> 2) take hugetlb lock and clear destructor for all pages on the list
> 3) free all pages on list back to low level allocators
> 
> Signed-off-by: Mike Kravetz <mike.kravetz@...cle.com>

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

Thanks.