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SubjectRe: [PATCH v7 0/5] Free the 2nd vmemmap page associated with each HugeTLB page
On Wed, Nov 24, 2021 at 11:09 AM Andrew Morton
<akpm@linux-foundation.org> wrote:
>
> On Mon, 22 Nov 2021 12:21:32 +0800 Muchun Song <songmuchun@bytedance.com> wrote:
>
> > On Wed, Nov 10, 2021 at 2:18 PM Muchun Song <songmuchun@bytedance.com> wrote:
> > >
> > > On Tue, Nov 9, 2021 at 3:33 AM Mike Kravetz <mike.kravetz@oracle.com> wrote:
> > > >
> > > > On 11/8/21 12:16 AM, Muchun Song wrote:
> > > > > On Mon, Nov 1, 2021 at 11:22 AM Muchun Song <songmuchun@bytedance.com> wrote:
> > > > >>
> > > > >> This series can minimize the overhead of struct page for 2MB HugeTLB pages
> > > > >> significantly. It further reduces the overhead of struct page by 12.5% for
> > > > >> a 2MB HugeTLB compared to the previous approach, which means 2GB per 1TB
> > > > >> HugeTLB. It is a nice gain. Comments and reviews are welcome. Thanks.
> > > > >>
> > > > >
> > > > > Hi,
> > > > >
> > > > > Ping guys. Does anyone have any comments or suggestions
> > > > > on this series?
> > > > >
> > > > > Thanks.
> > > > >
> > > >
> > > > I did look over the series earlier. I have no issue with the hugetlb and
> > > > vmemmap modifications as they are enhancements to the existing
> > > > optimizations. My primary concern is the (small) increased overhead
> > > > for the helpers as outlined in your cover letter. Since these helpers
> > > > are not limited to hugetlb and used throughout the kernel, I would
> > > > really like to get comments from others with a better understanding of
> > > > the potential impact.
> > >
> > > Thanks Mike. I'd like to hear others' comments about this as well.
> > > From my point of view, maybe the (small) overhead is acceptable
> > > since it only affects the head page, however Matthew Wilcox's folio
> > > series could reduce this situation as well.
>
> I think Mike was inviting you to run some tests to quantify the
> overhead ;)

Hi Andrew,

Sorry for the late reply.

Specific overhead figures are already in the cover letter. Also,
I did some other tests, e.g. kernel compilation, sysbench. I didn't
see any regressions.

>
> > Ping guys.
> >
> > Hi Andrew,
> >
> > Do you have any suggestions on this series to move it on?
> >
>
> I tossed it in there for some testing but yes please, additional
> reviewing?

It's already been in the next-tree (also in our ByteDance servers)
for several months, and I didn't receive any negative feedback.

Do you think it is ready for 5.17?

Thanks.

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