linux-kernel - Re: Widespread crashes in -next, bisected to 'mm: drop HASH

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Date:   Sat, 20 May 2017 07:21:56 -0700
From:   Guenter Roeck <linux@...ck-us.net>
To:     Michal Hocko <mhocko@...nel.org>
Cc:     linux-kernel@...r.kernel.org,
        Pavel Tatashin <pasha.tatashin@...cle.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Stephen Rothwell <sfr@...b.auug.org.au>,
        Kevin Hilman <khilman@...libre.com>
Subject: Re: Widespread crashes in -next, bisected to 'mm: drop HASH_ADAPT'

On 05/20/2017 12:26 AM, Michal Hocko wrote:
> On Fri 19-05-17 09:46:23, Guenter Roeck wrote:
>> Hi,
>>
>> my qemu tests of next-20170519 show the following results:
>> 	total: 122 pass: 30 fail: 92
>>
>> I won't bother listing all of the failures; they are available at
>> http://kerneltests.org/builders. I bisected one (openrisc, because
>> it gives me some console output before dying). It points to
>> 'mm: drop HASH_ADAPT' as the culprit. Bisect log is attached.
>>
>> A quick glance suggests that 64 bit kernels pass and 32 bit kernels fail.
>> 32-bit x86 images fail and should provide an easy test case.
> 
> Hmm, this is quite unexpected as the patch is not supposed to change
> things much. It just removes the flag and perform the new hash scaling

It may well be that the problem is introduced with an earlier patch and just
enabled by this one.

> automatically for all requeusts which do not have any high limit.
> Some of those didn't have HASH_ADAPT before but that shouldn't change
> the picture much. The only thing that I can imagine is that what
> formerly failed for early memblock allocations is now suceeding and that
> depletes the early memory. Do you have any serial console from the boot?
> 

They are all the same. Either nothing or the following. Picking a couple:

metag:

Linux version 4.12.0-rc1-next-20170519 (groeck@...iter.roeck-us.net) (gcc version 4.2.4 (IMG-1.4.0.300)) #1 Fri May 19 00:50:50 PDT 2017
LNKGET/SET go through cache but CONFIG_METAG_LNKGET_AROUND_CACHE=y
DA present
console [ttyDA1] enabled
OF: fdt: Machine model: toumaz,tz1090
Machine name: Generic Meta
Node 0: start_pfn = 0xb0000, low = 0xbfff7
Zone ranges:
   Normal   [mem 0x00000000b0000000-0x00000000bfff6fff]
Movable zone start for each node
Early memory node ranges
   node   0: [mem 0x00000000b0000000-0x00000000bfff6fff]
Initmem setup node 0 [mem 0x00000000b0000000-0x00000000bfff6fff]
Built 1 zonelists in Zone order, mobility grouping on.  Total pages: 65015
Kernel command line: rdinit=/sbin/init doreboot
PID hash table entries: 1024 (order: 0, 4096 bytes)

crisv32:

Linux version 4.12.0-rc1-next-20170519 (groeck@...ktop.roeck-us.net) (gcc version 4.9.2 (Buildroot 2015.02-rc1-00005-gb13bd8e-dirty) ) #1 Fri May 19 00:52:55 PDT 2017
bootconsole [early0] enabled
Setting up paging and the MMU.
Linux/CRISv32 port on ETRAX FS (C) 2003, 2004 Axis Communications AB
Built 1 zonelists in Zone order, mobility grouping on.  Total pages: 4080
Kernel command line: console=ttyS0,115200,N,8 rdinit=/sbin/init
PID hash table entries: 128 (order: -4, 512 bytes)

powerpc:mpc8548cds:

Memory CAM mapping: 256 Mb, residual: 0Mb
Linux version 4.12.0-rc1-next-20170519 (groeck@...iter.roeck-us.net) (gcc version 4.8.1 (GCC) ) #1 Fri May 19 01:17:29 PDT 2017
Found initrd at 0xc4000000:0xc4200c00
Using MPC85xx CDS machine description
bootconsole [udbg0] enabled
-----------------------------------------------------
phys_mem_size     = 0x10000000
dcache_bsize      = 0x20
icache_bsize      = 0x20
cpu_features      = 0x0000000012100460
   possible        = 0x0000000012100460
   always          = 0x0000000000100000
cpu_user_features = 0x84e08000 0x08000000
mmu_features      = 0x00020010
-----------------------------------------------------
mpc85xx_cds_setup_arch()
Could not find FPGA node.
Zone ranges:
   DMA      [mem 0x0000000000000000-0x000000000fffffff]
   Normal   empty
Movable zone start for each node
Early memory node ranges
   node   0: [mem 0x0000000000000000-0x000000000fffffff]
Initmem setup node 0 [mem 0x0000000000000000-0x000000000fffffff]
MMU: Allocated 1088 bytes of context maps for 255 contexts
Built 1 zonelists in Zone order, mobility grouping on.  Total pages: 65024
Kernel command line: rdinit=/sbin/init console=ttyS0 console=tty doreboot
PID hash table entries: 1024 (order: 0, 4096 bytes)

Guenter