RE: Low memory killer problem

[<zhiyuan_zhu@htc.com>]

Dear Greg, 

Very sorry my mail history is lost.

I found a part of ION memory will be return to system in android platform,
But these memorys  can’t accounted in low-memory-killer strategy.
…
And I also found ION memory comes from,  kmalloc/vmalloc/alloc pages/reserved memory.
I understand reserved memory shouldn't accounted to free memory.
But the memory which alloced by kmalloc/vmalloc/alloc pages, can be reclaimed.

But the low-memory killer can't accounted this part,
Many thanks.

Code location, 
   ---> drivers/staging/android/lowmemorykiller.c   -> lowmem_scan

Code review,
415         other_free = global_page_state(NR_FREE_PAGES);
416 
417         if (global_page_state(NR_SHMEM) + global_page_state(NR_MLOCK) + total_swapcache_pages() <
418                 global_page_state(NR_FILE_PAGES) + zcache_pages())
419                 other_file = global_page_state(NR_FILE_PAGES) + zcache_pages() -
420                                                 global_page_state(NR_SHMEM) -
422                                                 total_swapcache_pages();

So, other_free means:  MemFree,
other_file means: Buffers + Cached - ShMEM - SwapCache.
And part of  ( IonInUse - IonTotal ) should be reclaimed but not accounted.
Thanks.

Meminfo example
$ adb shell cat /proc/meminfo
MemTotal:        3805312 kB
MemFree:         1446220 kB
MemAvailable:    2388384 kB
Buffers:           16796 kB
Cached:          1190868 kB
…
IonTotal:         224252 kB
IonInUse:         199108 kB


Thanks
BR
Zhiyuan zhu

-----Original Message-----
From: Greg KH [mailto:gregkh@linuxfoundation.org] 
Sent: Monday, May 15, 2017 4:06 PM
To: Zhiyuan Zhu(朱志遠)
Cc: vinmenon@codeaurora.org; linux-mm@kvack.org; skhiani@codeaurora.org; torvalds@linux-foundation.org
Subject: Re: Low memory killer problem

On Mon, May 15, 2017 at 07:25:20AM +0000, zhiyuan_zhu@htc.com wrote:
> Loop MM maintainers,
> 
>  
> 
> Dear All,
> 
>  
> 
> Who can talk about this problem? Thanks.

What problem?

> Maybe this is lowmemory killer’s bug ?

This code is now removed from the kernel, so I doubt there could be a bug in it :)

> ION memory is complex now, we need to have a breakdown for them, I think.

What do you mean by this?

thanks,

greg k-h