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Date:   Mon, 16 Mar 2020 10:31:54 +0200
From:   Leon Romanovsky <leon@kernel.org>
To:     Jaewon Kim <jaewon31.kim@samsung.com>
Cc:     Vlastimil Babka <vbabka@suse.cz>, 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>
Subject: Re: [RFC PATCH 0/3] meminfo: introduce extra meminfo
Message-ID: <20200316083154.GF8510@unreal>
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On Mon, Mar 16, 2020 at 01:07:08PM +0900, Jaewon Kim wrote:
>
>
> 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.

It is more than enough :).

>
> 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?

Thanks

>
> Thank you
> Jaewon Kim