linux-kernel - RE: [PATCH 0/8] memblock: introduce memsize showing reserved memory

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Message-ID: <20220329024620epcms1p7633018e83f54e532761008a60da5254f@epcms1p7>
Date:   Tue, 29 Mar 2022 11:46:20 +0900
From:   Jaewon Kim <jaewon31.kim@...sung.com>
To:     Mike Rapoport <rppt@...nel.org>,
        Jaewon Kim <jaewon31.kim@...sung.com>
CC:     "vbabka@...e.cz" <vbabka@...e.cz>,
        "akpm@...ux-foundation.org" <akpm@...ux-foundation.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        "linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
        YongTaek Lee <ytk.lee@...sung.com>,
        "jaewon31.kim@...il.com" <jaewon31.kim@...il.com>
Subject: RE: [PATCH 0/8] memblock: introduce memsize showing reserved memory

>> > 
>> >--------- Original Message ---------
>> >Sender : Mike Rapoport <rppt@...nel.org>
>> >Date : 2022-03-27 16:40 (GMT+9)
>> >Title : Re: [PATCH 0/8] memblock: introduce memsize showing reserved memory
>> > 
>> > 
>> >I'm still not following. The reserved region sizes are available in the
>> >existing memblock debugfs.
>> >Why the names are important? What is the value of having names for *some*
>> >of the reserved regions?
>> 
>> Hi
>> 
>> There are many memory regions in memblock debugfs memory/reserved, and some might
>> be splited or merged with other region. Among regions in debugfs, we can't find 
>> the one we defined in device tree. Especially it is difficult to find the region we
>> described size only without start address.
>> 
>> On mobile environment, memory is used by not only CPU but also GPU, Camera, Secure
>> world, Audio, ETC. To support them, there are many reserved regions described in
>> device tree. So the name is quite important to recognize a region. And with thename
>> we can compare reserved memory map with other map.
>
>You still didn't describe your use case. What is the problem your patches
>are trying to solve? Why is it important to know what is the use of particular
>reserved region? 
>
>You propose complex mechanism that seems to fit very particular scenario
>and sprinkle some calls to this mechanism at random places because you need
>to "compare reserved memory map with other map".
>
>Does not sound convincing to me, sorry.

As I said serveral times, I want a simple knob showing all reserved memory status.
The current debugfs, device tree do not show all those information I want. I think you also know that.
 i.e. late freed pages, splited or merged memblock, address defined at boot time, kernel size, ETC. 

Anyway I think I touched too many points to do this. Let me drop this.

>
>> Thank you
>> Jaewon Kim
>
>-- 
>Sincerely yours,
>Mike.
>