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

2020년 3월 16일 (월) 오후 5:32, Leon Romanovsky [off-list ref]님이 작성:

On Mon, Mar 16, 2020 at 01:07:08PM +0900, Jaewon Kim wrote:

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On 2020년 03월 14일 02:48, Leon Romanovsky wrote:

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On Fri, Mar 13, 2020 at 04:19:36PM +0100, Vlastimil Babka wrote:

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+CC linux-api, please include in future versions as well

On 3/11/20 4:44 AM, Jaewon Kim wrote:

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/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.

It is more than enough :).

quoted

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.

Can you please help me to understand how that file will look like once
many drivers will start to use this interface? Will I see multiple
lines?

Something like:
driver1 ....
driver2 ....
driver3 ....
...
driver1000 ....

How can we extend it to support subsystems core code?

I do not have a plan to support subsystem core.

I just want the /proc/meminfo_extra to show size of alloc_pages APIs
rather than slub size. It is to show hidden huge memory.
I think most of drivers do not need to register its size to
/proc/meminfo_extra because
drivers usually use slub APIs and rather than alloc_pages APIs.
/proc/slabinfo helps for slub size in detail.

As a candidate of /proc/meminfo_extra, I hope only few drivers using
huge memory like over 100 MB got from alloc_pages APIs.

As you say, if there is a static node on /sys for each driver, it may
be used for all the drivers.
I think sysfs class way may be better to show categorized sum size.
But /proc/meminfo_extra can be another way to show those hidden huge memory.
I mean your idea and my idea is not exclusive.

Thank you

Thanks

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Thank you
Jaewon Kim