linux-kernel - Re: [RFC PATCH v2 0/3] meminfo_extra: introduce meminfo extra

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Message-ID: <20200325181255.GB18706@avx2>
Date:   Wed, 25 Mar 2020 21:12:55 +0300
From:   Alexey Dobriyan <adobriyan@...il.com>
To:     Jaewon Kim <jaewon31.kim@...sung.com>
Cc:     gregkh@...uxfoundation.org, leon@...nel.org, vbabka@...e.cz,
        akpm@...ux-foundation.org, labbott@...hat.com,
        sumit.semwal@...aro.org, minchan@...nel.org, ngupta@...are.org,
        sergey.senozhatsky.work@...il.com, kasong@...hat.com,
        bhe@...hat.com, linux-mm@...ck.org, linux-kernel@...r.kernel.org,
        jaewon31.kim@...il.com, linux-api@...r.kernel.org,
        kexec@...ts.infradead.org
Subject: Re: [RFC PATCH v2 0/3] meminfo_extra: introduce meminfo extra

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