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

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Message-ID: <F28E23D0-C635-4A49-91EE-100AAA8C9EAD@fb.com>
Date:   Wed, 10 Aug 2022 17:14:37 +0000
From:   "Alex Zhu (Kernel)" <alexlzhu@...com>
To:     Yang Shi <shy828301@...il.com>
CC:     Yu Zhao <yuzhao@...gle.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>
Subject: Re: [PATCH v3] mm: add thp_utilization metrics to
 /proc/thp_utilization


> 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?