linux-kernel - Re: [PATCH] Revert "mm/cma: manage the memory of the CMA area by using the ZONE

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Date:   Thu, 17 May 2018 19:21:28 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Ville Syrjälä <ville.syrjala@...ux.intel.com>
Cc:     Joonsoo Kim <iamjoonsoo.kim@....com>,
        "Aneesh Kumar K . V" <aneesh.kumar@...ux.vnet.ibm.com>,
        Tony Lindgren <tony@...mide.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Johannes Weiner <hannes@...xchg.org>,
        Laura Abbott <lauraa@...eaurora.org>,
        Marek Szyprowski <m.szyprowski@...sung.com>,
        Mel Gorman <mgorman@...hsingularity.net>,
        Michal Nazarewicz <mina86@...a86.com>,
        Minchan Kim <minchan@...nel.org>,
        Rik van Riel <riel@...hat.com>,
        Russell King <linux@...linux.org.uk>,
        Will Deacon <will.deacon@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        linux-mm@...ck.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] Revert "mm/cma: manage the memory of the CMA area by
 using the ZONE_MOVABLE"

On Thu 17-05-18 20:13:35, Ville Syrjälä wrote:
> On Thu, May 17, 2018 at 06:49:47PM +0200, Michal Hocko wrote:
> > On Thu 17-05-18 16:58:32, Ville Syrjälä wrote:
> > > On Thu, May 17, 2018 at 04:36:29PM +0300, Ville Syrjälä wrote:
> > > > On Thu, May 17, 2018 at 03:21:09PM +0200, Michal Hocko wrote:
> > > > > On Thu 17-05-18 15:59:59, Ville Syrjala wrote:
> > > > > > From: Ville Syrjälä <ville.syrjala@...ux.intel.com>
> > > > > > 
> > > > > > This reverts commit bad8c6c0b1144694ecb0bc5629ede9b8b578b86e.
> > > > > > 
> > > > > > Make x86 with HIGHMEM=y and CMA=y boot again.
> > > > > 
> > > > > Is there any bug report with some more details? It is much more
> > > > > preferable to fix the issue rather than to revert the whole thing
> > > > > right away.
> > > > 
> > > > The machine I have in front of me right now didn't give me anything.
> > > > Black screen, and netconsole was silent. No serial port on this
> > > > machine unfortunately.
> > > 
> > > Booted on another machine with serial:
> > 
> > Could you provide your .config please?
> 
> Attached. Not sure there's anything particularly useful in it though
> since I've now seen this on all the highmem systems I've booted.

It has CONFIG_HAVE_MEMBLOCK_NODE_MAP so the movable_zone initialization
depends on quite some crazy movable init code paths. So maybe that is
the place to look at.
 
 
> BTW I just noticed that the reported memory sizes look pretty crazy:
> 
> Memory: 3926480K/3987424K available (5254K kernel code, 561K rwdata,
> 2156K rodata, 572K init, 9308K bss, 56848K reserved,
> 4096K cma-reserved, 3078532K highmem)
> 
> vs.
> 
> Memory: 7001976K/3987424K available (5254K kernel code, 561K rwdata,
> 2156K rodata, 572K init, 9308K bss, 4291097664K reserved,
> 4096K cma-reserved, 7005012K highmem)

This smells like a fallout. Reserved pages clearly underflowed which
suggested we are initializating more than we should.
-- 
Michal Hocko
SUSE Labs