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

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Date:   Mon, 10 Apr 2017 17:22:28 +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>,
        Martin Schwidefsky <schwidefsky@...ibm.com>,
        Tobias Regnery <tobias.regnery@...il.com>
Subject: Re: [PATCH -v2 0/9] mm: make movable onlining suck less

[dropping Lai Jiangshan whose email bounces]

On Mon 10-04-17 16:56:39, Michal Hocko wrote:
> 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.

Heh, this one is embarrassing
diff --git a/drivers/base/memory.c b/drivers/base/memory.c
index 1c6fdacbccd3..9677b6b711b0 100644
--- a/drivers/base/memory.c
+++ b/drivers/base/memory.c
@@ -402,7 +402,7 @@ static ssize_t show_valid_zones(struct device *dev,
 		return sprintf(buf, "none\n");
 
 	start_pfn = valid_start_pfn;
-	nr_pages = valid_end_pfn - valid_end_pfn;
+	nr_pages = valid_end_pfn - start_pfn;
 
 	/*
 	 * Check the existing zone. Make sure that we do that only on the
-- 
Michal Hocko
SUSE Labs