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Subject: Re: [RFC PATCH 0/3] meminfo: introduce extra meminfo
To:     Leon Romanovsky <leon@kernel.org>, Vlastimil Babka <vbabka@suse.cz>
Cc:     adobriyan@gmail.com, akpm@linux-foundation.org, labbott@redhat.com,
        sumit.semwal@linaro.org, minchan@kernel.org, ngupta@vflare.org,
        sergey.senozhatsky.work@gmail.com, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org, jaewon31.kim@gmail.com,
        Linux API <linux-api@vger.kernel.org>
From:   Jaewon Kim <jaewon31.kim@samsung.com>
Message-ID: <5E6EFB6C.7050105@samsung.com>
Date:   Mon, 16 Mar 2020 13:07:08 +0900
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On 2020년 03월 14일 02:48, Leon Romanovsky wrote:
> On Fri, Mar 13, 2020 at 04:19:36PM +0100, Vlastimil Babka wrote:
>> +CC linux-api, please include in future versions as well
>>
>> On 3/11/20 4:44 AM, 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
>> I like the idea and the dynamic nature of this, so that drivers not present
>> wouldn't add lots of useless zeroes to the output.
>> It also makes simpler the decisions of "what is important enough to need its own
>> meminfo entry".
>>
>> The suggestion for hunting per-driver /sys files would only work if there was a
>> common name to such files so once can find(1) them easily.
>> It also doesn't work for the oom/failed alloc warning output.
> Of course there is a need to have a stable name for such an output, this
> is why driver/core should be responsible for that and not drivers authors.
>
> The use case which I had in mind slightly different than to look after OOM.
>
> I'm interested to optimize our drivers in their memory footprint to
> allow better scale in SR-IOV mode where one device creates many separate
> copies of itself. Those copies easily can take gigabytes of RAM due to
> the need to optimize for high-performance networking. Sometimes the
> amount of memory and not HW is actually limits the scale factor.
>
> So I would imagine this feature being used as an aid for the driver
> developers and not for the runtime decisions.
>
> My 2-cents.
>
> Thanks
>
>
Thank you for your comment.
My idea, I think, may be able to help each driver developer to see their memory usage.
But I'd like to see overall memory usage through the one node.

Let me know if you have more comment.
I am planning to move my logic to be shown on a new node, /proc/meminfo_extra at v2.

Thank you
Jaewon Kim