linux-kernel - Re: [External] Re: [PATCH v9 03/11] mm/hugetlb: Free the vmemmap pages associated with each HugeTLB page

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Date:   Wed, 16 Dec 2020 21:15:37 +0800
From:   Muchun Song <songmuchun@...edance.com>
To:     Oscar Salvador <osalvador@...e.de>
Cc:     Jonathan Corbet <corbet@....net>,
        Mike Kravetz <mike.kravetz@...cle.com>,
        Thomas Gleixner <tglx@...utronix.de>, mingo@...hat.com,
        bp@...en8.de, x86@...nel.org, hpa@...or.com,
        dave.hansen@...ux.intel.com, luto@...nel.org,
        Peter Zijlstra <peterz@...radead.org>, viro@...iv.linux.org.uk,
        Andrew Morton <akpm@...ux-foundation.org>, paulmck@...nel.org,
        mchehab+huawei@...nel.org, pawan.kumar.gupta@...ux.intel.com,
        Randy Dunlap <rdunlap@...radead.org>, oneukum@...e.com,
        anshuman.khandual@....com, jroedel@...e.de,
        Mina Almasry <almasrymina@...gle.com>,
        David Rientjes <rientjes@...gle.com>,
        Matthew Wilcox <willy@...radead.org>,
        Michal Hocko <mhocko@...e.com>,
        "Song Bao Hua (Barry Song)" <song.bao.hua@...ilicon.com>,
        David Hildenbrand <david@...hat.com>,
        Xiongchun duan <duanxiongchun@...edance.com>,
        linux-doc@...r.kernel.org, LKML <linux-kernel@...r.kernel.org>,
        Linux Memory Management List <linux-mm@...ck.org>,
        linux-fsdevel <linux-fsdevel@...r.kernel.org>
Subject: Re: [External] Re: [PATCH v9 03/11] mm/hugetlb: Free the vmemmap
 pages associated with each HugeTLB page

On Wed, Dec 16, 2020 at 9:06 PM Oscar Salvador <osalvador@...e.de> wrote:
>
> On Sun, Dec 13, 2020 at 11:45:26PM +0800, Muchun Song wrote:
> > +
> > +/*
> > + * vmemmap_rmap_walk - walk vmemmap page table
> > + *
> > + * @rmap_pte:                called for each non-empty PTE (lowest-level) entry.
> > + * @reuse:           the page which is reused for the tail vmemmap pages.
> > + * @vmemmap_pages:   the list head of the vmemmap pages that can be freed.
> > + */
> > +struct vmemmap_rmap_walk {
> > +     void (*rmap_pte)(pte_t *pte, unsigned long addr,
> > +                      struct vmemmap_rmap_walk *walk);
> > +     struct page *reuse;
> > +     struct list_head *vmemmap_pages;
> > +};
>
> Why did you chose this approach in this version?
> Earlier versions of this patchset had a single vmemmap_to_pmd() function
> which returned the PMD, and now we have serveral vmemmap_{levels}_range
> and a vmemmap_rmap_walk.

This approach will be more universal. :-)

> A brief explanation about why this change was introduced would have been nice.
>
> I guess it is because ealier versions were too oriented for the usecase
> this patchset presents, while the new versions tries to be more broad
> about future re-uses of the interface?

Yeah, you are right. I plan to reuse those interfaces in the feature.

Thanks.

>
>
> --
> Oscar Salvador
> SUSE L3



-- 
Yours,
Muchun