On Mon, Mar 23, 2020 at 05:05:00PM +0900, Jaewon Kim wrote:

/proc/meminfo or show_free_areas does not show full system wide memory
usage status because memory stats do not track all memory allocations.
There seems to be huge hidden memory especially on embedded system. It
is because some HW IPs in the system use common DRAM memory instead of
internal memory. Device drivers directly request huge pages from the
page allocator with alloc_pages.

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 be useful if /proc/meminfo_extra shows all those extra memory
information. And show_mem also need to print the info in oom situation.

Fortunately vmalloc pages is already 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_meminfo_extra(atomic_long_t *val, int shift,
			   const char *name);
int unregister_meminfo_extra(atomic_long_t *val);

Currently register ION system heap allocator and zsmalloc pages.
Additionally tested on local graphics driver.

i.e) cat /proc/meminfo_extra | tail -3
IonSystemHeap:    242620 kB
ZsPages:          203860 kB
GraphicDriver:    196576 kB

In that case definitely delete ':', spaces and KB.
They only slowdown generation and parsing in userspace.
Values should be printed /proc/vmstat does it, maybe with tab instead of
space.

	foo	1234
	bar	0
	zot	111