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SubjectRE: [External] RE: [PATCH v4 00/21] Free some vmemmap pages of hugetlb page
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> -----Original Message-----
> From: Oscar Salvador [mailto:osalvador@suse.de]
> Sent: Wednesday, November 18, 2020 8:45 AM
> To: Muchun Song <songmuchun@bytedance.com>
> Cc: Song Bao Hua (Barry Song) <song.bao.hua@hisilicon.com>;
> corbet@lwn.net; mike.kravetz@oracle.com; tglx@linutronix.de;
> mingo@redhat.com; bp@alien8.de; x86@kernel.org; hpa@zytor.com;
> dave.hansen@linux.intel.com; luto@kernel.org; peterz@infradead.org;
> viro@zeniv.linux.org.uk; akpm@linux-foundation.org; paulmck@kernel.org;
> mchehab+huawei@kernel.org; pawan.kumar.gupta@linux.intel.com;
> rdunlap@infradead.org; oneukum@suse.com; anshuman.khandual@arm.com;
> jroedel@suse.de; almasrymina@google.com; rientjes@google.com;
> willy@infradead.org; mhocko@suse.com; duanxiongchun@bytedance.com;
> linux-doc@vger.kernel.org; linux-kernel@vger.kernel.org; linux-mm@kvack.org;
> linux-fsdevel@vger.kernel.org
> 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

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