linux-kernel - Re: [RFC PATCH 0/3] meminfo: introduce extra meminfo

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Message-ID: <5E6B0E72.7010305@samsung.com>
Date:   Fri, 13 Mar 2020 13:39:14 +0900
From:   Jaewon Kim <jaewon31.kim@...sung.com>
To:     Leon Romanovsky <leon@...nel.org>
Cc:     adobriyan@...il.com, akpm@...ux-foundation.org, labbott@...hat.com,
        sumit.semwal@...aro.org, minchan@...nel.org, ngupta@...are.org,
        sergey.senozhatsky.work@...il.com, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, jaewon31.kim@...il.com
Subject: Re: [RFC PATCH 0/3] meminfo: introduce extra meminfo



On 2020년 03월 11일 16:25, Leon Romanovsky wrote:
> On Wed, Mar 11, 2020 at 12:44:38PM +0900, Jaewon Kim wrote:
>> /proc/meminfo or show_free_areas does not show full system wide memory
>> usage status. There seems to be huge hidden memory especially on
>> embedded Android system. Because it usually have some HW IP which do not
>> have internal memory and use common DRAM memory.
>>
>> In Android system, most of those hidden memory seems to be vmalloc pages
>> , ion system heap memory, graphics memory, and memory for DRAM based
>> compressed swap storage. They may be shown in other node but it seems to
>> useful if /proc/meminfo shows all those extra memory information. And
>> show_mem also need to print the info in oom situation.
>>
>> Fortunately vmalloc pages is alread shown by commit 97105f0ab7b8
>> ("mm: vmalloc: show number of vmalloc pages in /proc/meminfo"). Swap
>> memory using zsmalloc can be seen through vmstat by commit 91537fee0013
>> ("mm: add NR_ZSMALLOC to vmstat") but not on /proc/meminfo.
>>
>> Memory usage of specific driver can be various so that showing the usage
>> through upstream meminfo.c is not easy. To print the extra memory usage
>> of a driver, introduce following APIs. Each driver needs to count as
>> atomic_long_t.
>>
>> int register_extra_meminfo(atomic_long_t *val, int shift,
>> 			   const char *name);
>> int unregister_extra_meminfo(atomic_long_t *val);
>>
>> Currently register ION system heap allocator and zsmalloc pages.
>> Additionally tested on local graphics driver.
>>
>> i.e) cat /proc/meminfo | tail -3
>> IonSystemHeap:    242620 kB
>> ZsPages:          203860 kB
>> GraphicDriver:    196576 kB
>>
>> i.e.) show_mem on oom
>> <6>[  420.856428]  Mem-Info:
>> <6>[  420.856433]  IonSystemHeap:32813kB ZsPages:44114kB GraphicDriver::13091kB
>> <6>[  420.856450]  active_anon:957205 inactive_anon:159383 isolated_anon:0
> The idea is nice and helpful, but I'm sure that the interface will be abused
> almost immediately. I expect that every driver will register to such API.
>
> First it will be done by "large" drivers and after that everyone will copy/paste.
I thought using it is up to driver developers.
If it is abused, /proc/meminfo will show too much info. for that device.
What about a new node, /proc/meminfo_extra, to gather those info. and not
corrupting original /proc/meminfo.

Thank you
> Thanks
>
>