linux-kernel - Re: [PATCH 2/6] mm: vmstat: move slab statistics from zone to node counters

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Date:   Wed, 31 May 2017 13:39:00 +0200
From:   Heiko Carstens <heiko.carstens@...ibm.com>
To:     Johannes Weiner <hannes@...xchg.org>,
        Josef Bacik <josef@...icpanda.com>,
        Michal Hocko <mhocko@...e.com>,
        Vladimir Davydov <vdavydov.dev@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Rik van Riel <riel@...hat.com>, linux-mm@...ck.org,
        cgroups@...r.kernel.org, linux-kernel@...r.kernel.org,
        kernel-team@...com, linux-s390@...r.kernel.org
Subject: Re: [PATCH 2/6] mm: vmstat: move slab statistics from zone to node
 counters

On Wed, May 31, 2017 at 11:12:56AM +0200, Heiko Carstens wrote:
> On Tue, May 30, 2017 at 02:17:20PM -0400, Johannes Weiner wrote:
> > To re-implement slab cache vs. page cache balancing, we'll need the
> > slab counters at the lruvec level, which, ever since lru reclaim was
> > moved from the zone to the node, is the intersection of the node, not
> > the zone, and the memcg.
> > 
> > We could retain the per-zone counters for when the page allocator
> > dumps its memory information on failures, and have counters on both
> > levels - which on all but NUMA node 0 is usually redundant. But let's
> > keep it simple for now and just move them. If anybody complains we can
> > restore the per-zone counters.
> > 
> > Signed-off-by: Johannes Weiner <hannes@...xchg.org>
> 
> This patch causes an early boot crash on s390 (linux-next as of today).
> CONFIG_NUMA on/off doesn't make any difference. I haven't looked any
> further into this yet, maybe you have an idea?
> 
> Kernel BUG at 00000000002b0362 [verbose debug info unavailable]
> addressing exception: 0005 ilc:3 [#1] SMP
> Modules linked in:
> CPU: 0 PID: 0 Comm: swapper Not tainted 4.12.0-rc3-00153-gb6bc6724488a #16
> Hardware name: IBM 2964 N96 702 (z/VM 6.4.0)
> task: 0000000000d75d00 task.stack: 0000000000d60000
> Krnl PSW : 0404200180000000 00000000002b0362 (mod_node_page_state+0x62/0x158)
>            R:0 T:1 IO:0 EX:0 Key:0 M:1 W:0 P:0 AS:0 CC:2 PM:0 RI:0 EA:3
> Krnl GPRS: 0000000000000001 000000003d81f000 0000000000000000 0000000000000006
>            0000000000000001 0000000000f29b52 0000000000000041 0000000000000000
>            0000000000000007 0000000000000040 000000003fe81000 000003d100ffa000
>            0000000000ee1cd0 0000000000979040 0000000000300abc 0000000000d63c90
> Krnl Code: 00000000002b0350: e31003900004 lg %r1,912
>            00000000002b0356: e320f0a80004 lg %r2,168(%r15)
>           #00000000002b035c: e31120000090 llgc %r1,0(%r1,%r2)
>           >00000000002b0362: b9060011  lgbr %r1,%r1
>            00000000002b0366: e32003900004 lg %r2,912
>            00000000002b036c: e3c280000090 llgc %r12,0(%r2,%r8)
>            00000000002b0372: b90600ac  lgbr %r10,%r12
>            00000000002b0376: b904002a  lgr %r2,%r10
> Call Trace:
> ([<0000000000000000>]           (null))
>  [<0000000000300abc>] new_slab+0x35c/0x628
>  [<000000000030740c>] __kmem_cache_create+0x33c/0x638
>  [<0000000000e99c0e>] create_boot_cache+0xae/0xe0
>  [<0000000000e9e12c>] kmem_cache_init+0x5c/0x138
>  [<0000000000e7999c>] start_kernel+0x24c/0x440
>  [<0000000000100020>] _stext+0x20/0x80
> Last Breaking-Event-Address:
>  [<0000000000300ab6>] new_slab+0x356/0x628

FWIW, it looks like your patch only triggers a bug that was introduced with
a different change that somehow messes around with the pages used to setup
the kernel page tables. I'll look into this.