linux-kernel - Re: [PATCH -v2 0/9] mm: make movable onlining suck less

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Date:   Mon, 10 Apr 2017 16:56:39 +0200
From:   Michal Hocko <mhocko@...nel.org>
To:     Igor Mammedov <imammedo@...hat.com>
Cc:     linux-mm@...ck.org, Andrew Morton <akpm@...ux-foundation.org>,
        Mel Gorman <mgorman@...e.de>, Vlastimil Babka <vbabka@...e.cz>,
        Andrea Arcangeli <aarcange@...hat.com>,
        Jerome Glisse <jglisse@...hat.com>,
        Reza Arbab <arbab@...ux.vnet.ibm.com>,
        Yasuaki Ishimatsu <yasu.isimatu@...il.com>,
        qiuxishi@...wei.com, Kani Toshimitsu <toshi.kani@....com>,
        slaoub@...il.com, Joonsoo Kim <js1304@...il.com>,
        Andi Kleen <ak@...ux.intel.com>,
        David Rientjes <rientjes@...gle.com>,
        Daniel Kiper <daniel.kiper@...cle.com>,
        Vitaly Kuznetsov <vkuznets@...hat.com>,
        LKML <linux-kernel@...r.kernel.org>,
        Dan Williams <dan.j.williams@...il.com>,
        Heiko Carstens <heiko.carstens@...ibm.com>,
        Lai Jiangshan <laijs@...fujitsu.com>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Tobias Regnery <tobias.regnery@...il.com>
Subject: Re: [PATCH -v2 0/9] mm: make movable onlining suck less

On Mon 10-04-17 16:27:49, Igor Mammedov wrote:
[...]
> Hi Michal,
> 
> I've given series some dumb testing, see below for unexpected changes I've noticed.
> 
> Using the same CLI as above plus hotpluggable dimms present at startup
> (it still uses hotplug path as dimms aren't reported in e820)
> 
> -object memory-backend-ram,id=mem1,size=256M -object memory-backend-ram,id=mem0,size=256M \
> -device pc-dimm,id=dimm1,memdev=mem1,slot=1,node=0 -device pc-dimm,id=dimm0,memdev=mem0,slot=0,node=0
> 
> so dimm1 => memory3[23] and dimm0 => memory3[45]
> 
> #issue1:
> unable to online memblock as NORMAL adjacent to onlined MOVABLE
> 
> 1: after boot
> memory32:offline removable: 0  zones: Normal Movable
> memory33:offline removable: 0  zones: Normal Movable
> memory34:offline removable: 0  zones: Normal Movable
> memory35:offline removable: 0  zones: Normal Movable
> 
> 2: online as movable 1st dimm
> 
> #echo online_movable > memory32/state
> #echo online_movable > memory33/state
> 
> everything is as expected:
> memory32:online removable: 1  zones: Movable
> memory33:online removable: 1  zones: Movable
> memory34:offline removable: 0  zones: Movable
> memory35:offline removable: 0  zones: Movable
> 
> 3: try to offline memory32 and online as NORMAL
> 
> #echo offline > memory32/state
> memory32:offline removable: 1  zones: Normal Movable
> memory33:online removable: 1  zones: Movable
> memory34:offline removable: 0  zones: Movable
> memory35:offline removable: 0  zones: Movable

OK, this is not expected. We are not shifting zones anymore so the range
which was online_movable will not become available to the zone Normal.
So this must be something broken down the show_valid_zones path. I will
investigate.

> 
> #echo online_kernel > memory32/state
> write error: Invalid argument
> // that's not what's expected

this is proper behavior with the current implementation. Does anything
depend on the zone reusing?

> memory32:offline removable: 1  zones: Normal Movable
> memory33:online removable: 1  zones: Movable
> memory34:offline removable: 0  zones: Movable
> memory35:offline removable: 0  zones: Movable
> 
> 
> ======
> #issue2: dimm1 assigned to node 1 on qemu CLI
> memblock is onlined as movable by default
> 
> // after boot
> memory32:offline removable: 1  zones: Normal
> memory33:offline removable: 1  zones: Normal Movable
> memory34:offline removable: 1  zones: Normal
> memory35:offline removable: 1  zones: Normal Movable
> // not related to this issue but notice not all blocks are
> // "Normal Movable" when compared when both dimms on node 0 /#issue1/

yes they should be

> #echo online_movable > memory33/state
> #echo online > memory32/state
> 
> memory32:online removable: 1  zones: Movable
> memory33:online removable: 1  zones: Movable
> 
> before series memory32 goes to zone NORMAL as expected
> memory32:online removable: 0  zones: Normal Movable
> memory33:online removable: 1  zones: Movable Normal

OK, I will double check.
 
> ======
> #issue3:
> removable flag flipped to non-removable state
> 
> // before series at commit ef0b577b6:
> memory32:offline removable: 0  zones: Normal Movable
> memory33:offline removable: 0  zones: Normal Movable
> memory34:offline removable: 0  zones: Normal Movable
> memory35:offline removable: 0  zones: Normal Movable
> 
> // after series at commit 6a010434
> memory32:offline removable: 1  zones: Normal
> memory33:offline removable: 1  zones: Normal
> memory34:offline removable: 1  zones: Normal
> memory35:offline removable: 1  zones: Normal Movable
> 
> also looking at #issue1 removable flag state doesn't
> seem to be consistent between state changes but maybe that's
> been broken before

OK, will have a look.

Thanks for your testing!

-- 
Michal Hocko
SUSE Labs