linux-kernel - Re: [PATCH] ARM: print cma-reserved pages from show

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Message-ID: <20150410112430.GB12732@n2100.arm.linux.org.uk>
Date:	Fri, 10 Apr 2015 12:24:31 +0100
From:	Russell King - ARM Linux <linux@....linux.org.uk>
To:	"Wang, Yalin" <Yalin.Wang@...ymobile.com>
Cc:	'Gregory Fong' <gregory.0xf0@...il.com>,
	Mel Gorman <mgorman@...e.de>,
	Laura Abbott <lauraa@...eaurora.org>,
	Florian Fainelli <f.fainelli@...il.com>,
	Kees Cook <keescook@...omium.org>,
	Nicolas Pitre <nico@...aro.org>,
	Catalin Marinas <catalin.marinas@....com>,
	open list <linux-kernel@...r.kernel.org>,
	"linux-arm-kernel@...ts.infradead.org" 
	<linux-arm-kernel@...ts.infradead.org>,
	"vishnu.ps@...sung.com" <vishnu.ps@...sung.com>,
	Marek Szyprowski <m.szyprowski@...sung.com>,
	Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH] ARM: print cma-reserved pages from show_mem

On Fri, Apr 10, 2015 at 01:18:04PM +0800, Wang, Yalin wrote:
> > [   12.212102] active_anon:734 inactive_anon:1189 isolated_anon:0
> > [   12.212102]  active_file:0 inactive_file:0 isolated_file:0
> > [   12.212102]  unevictable:0 dirty:0 writeback:0 unstable:0
> > [   12.212102]  free:254104 slab_reclaimable:82 slab_unreclaimable:843

Here, we have 82 pages reclaimable, which is 328kB, and 843 unreclaimable
which is 3372kB, which is a total of 925 pages.

> > [   12.212102]  mapped:429 shmem:1815 pagetables:13 bounce:0
> > [   12.212102]  free_cma:4032
> > [   12.243172] DMA free:754080kB min:3472kB low:4340kB high:5208kB
> > active_anon:180kB inactive_anon:0kB active_file:0kB inactive_file:0kB
> > unevictable:0kB isolated(anon):0kB isolated(file):0kB present:778240kB
> > managed:759252kB mlocked:0kB dirty:0kB writeback:0kB mapped:0kB
> > shmem:0kB slab_reclaimable:328kB slab_unreclaimable:3372kB

Which agrees here.

> > [   12.401609] 834 slab pages

but not here... this is an interesting difference, because in the ARM
version of show_mem(), we count the actual number of pages where
PageSlab() returns true.  Can slab pages also be reserved pages or
swap cache pages?  I thought they were exclusive of those.  So, the
question comes... why the difference in accounting, and which one is
correct.

Maybe there's a bug in the accounting somewhere...

So I think we're not ready for this patch to be merged yet.

-- 
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