RE: [External] RE: [PATCH v4 00/21] Free some vmemmap pages of hugetlb page

[Song Bao Hua (Barry Song)]

> -----Original Message-----
> From: Oscar Salvador [mailto:osalvador@xxxxxxx]
> Sent: Wednesday, November 18, 2020 8:45 AM
> To: Muchun Song <songmuchun@xxxxxxxxxxxxx>
> Cc: Song Bao Hua (Barry Song) <song.bao.hua@xxxxxxxxxxxxx>;
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> Subject: Re: [External] RE: [PATCH v4 00/21] Free some vmemmap pages of
> hugetlb page
> 
> On 2020-11-17 17:29, Muchun Song wrote:
> > Now for the 2MB HugrTLB page, we only free 6 vmemmap pages.
> > But your words woke me up. Maybe we really can free 7 vmemmap
> > pages. In this case, we can see 8 of the 512 struct page structures
> > has beed set PG_head flag. If we can adjust compound_head()
> > slightly and make compound_head() return the real head struct
> > page when the parameter is the tail struct page but with PG_head
> > flag set. I will start an investigation and a test.
> 
> I would not overcomplicate things at this stage, but rather keep it
> simple as the code is already tricky enough(without counting the LOC
> thatvit adds).
> We can always build on top later on in order to improve things.

Yep. I am not expecting freeing tail page to be done at this stage. This could
be something in the todo list after the first patchset is solid.

> 
> --
> Oscar Salvador
> SUSE L3

Thanks
Barry