linux-kernel - Re: [PATCH v3] mm: add thp_utilization metrics to /proc/thp

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Date:   Wed, 10 Aug 2022 11:54:09 -0600
From:   Yu Zhao <yuzhao@...gle.com>
To:     "Alex Zhu (Kernel)" <alexlzhu@...com>
Cc:     Yang Shi <shy828301@...il.com>, Rik van Riel <riel@...com>,
        Kernel Team <Kernel-team@...com>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "willy@...radead.org" <willy@...radead.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        Ning Zhang <ningzhang@...ux.alibaba.com>,
        Miaohe Lin <linmiaohe@...wei.com>
Subject: Re: [PATCH v3] mm: add thp_utilization metrics to /proc/thp_utilization

On Wed, Aug 10, 2022 at 11:15 AM Alex Zhu (Kernel) <alexlzhu@...com> wrote:
>
>
> > On Aug 10, 2022, at 10:07 AM, Yang Shi <shy828301@...il.com> wrote:
> >
> > On Tue, Aug 9, 2022 at 4:36 PM Yu Zhao <yuzhao@...gle.com> wrote:
> >>
> >> On Tue, Aug 9, 2022 at 11:16 AM Alex Zhu (Kernel) <alexlzhu@...com> wrote:
> >>>
> >>>
> >>>> OK, it is hard to tell what it looks like now. But the THPs on the
> >>>> deferred split list may be on the "low utilization split" list too?
> >>>> IIUC the major difference is to replace zero-filled subpage to special
> >>>> zero page, so you implemented another THP split function to handle it?
> >>>>
> >>>> Anyway the code should answer the most questions.
> >>>
> >>> They can indeed end up on both lists. This did have to be handled when
> >>> implementing the shrinker.
> >>>
> >>> We free the zero filled subpages, while modifying the existing split_huge_page()
> >>> function. Will follow up that change in another patch.
> >>
> >> FYI. This series does it:
> >>
> >> https://lore.kernel.org/r/20210731063938.1391602-1-yuzhao@google.com/
> >>
> >> And this one:
> >>
> >> https://lore.kernel.org/r/1635422215-99394-1-git-send-email-ningzhang@linux.alibaba.com/
> >
> > Thanks, Yu. I totally forgot about these series. It is time to refresh
> > my memory.
>
> I looked through these patches yesterday. There are indeed parts that are very similar, but the approach
> taken seems overly complicated compared to what I have written. What’s the status of work on this since last year?

Overly complicated... which patches and how?

At a minimum, you'd need 1 & 3 from the first series and this patch:

https://lore.kernel.org/r/20220608141432.23258-1-linmiaohe@huawei.com/