Re: swap_info_get: Bad swap offset entry 0200f8a7

From: huang ying <huang.ying.caritas@gmail.com>
To: Christian Kujau <lists@nerdbynature.de>
Cc: LKML <linux-kernel@vger.kernel.org>,
	Hugh Dickins <hughd@google.com>, Minchan Kim <minchan@kernel.org>,
	Nitin Gupta <ngupta@vflare.org>,
	Robert Schelander <rschelander@aon.at>
Subject: Re: swap_info_get: Bad swap offset entry 0200f8a7
Date: Sun, 22 Oct 2017 00:07:58 +0800	[thread overview]
Message-ID: <CAC=cRTMYgJ2mVrMdtS6=ofvzxHLA2K9YiWrhQwZHvLO=N_=HRQ@mail.gmail.com> (raw)
In-Reply-To: <alpine.DEB.2.21.9.1710201744330.31397@trent.utfs.org>

On Sat, Oct 21, 2017 at 9:07 AM, Christian Kujau <lists@nerdbynature.de> wrote:
> On Fri, 20 Oct 2017, huang ying wrote:
>> >       4 May  < Linux version 4.11.2-1-ARCH
>> >       4 Jun  < Linux version 4.11.3-1-ARCH
>> >       7 Jul  < Linux version 4.11.9-1-ARCH
>> >       4 Aug  < Linux version 4.12.8-2-ARCH
>> >      24 Sep  < Linux version 4.12.13-1-ARCH
>> >     158 Oct  < Linux version 4.13.5-1-ARCH
>>
>> So you have never seen this before 4.11 like 4.10?
>
> Unfortunately the kernel logs for that machine only go back until May
> 2017 and I cannot tell if that hasn't happened before. I've seen these
> messages appear since then but didn't bother much. But as it now happens
> more frequently, I thought I should mention this to the list.
>
>> Which operations will trigger this error messages?
>
> I'm not able to reproduce it at will, but I suspect that memory pressure
> triggers these messages. The machine in question is an Lenovo Ideapad S10
> notebook running 24x7 and is equipped with 1 GB of RAM. Two Java processes
> are basically using up all the memory, so usually it tooks like this:
>
> ========================================
> $ free -m
>        total   used  free   shared  buff/cache available
> Mem:     994    866    67       1           60        20
> Swap:    760    437   322
>
> $ zramctl
> NAME       ALGORITHM DISKSIZE  DATA COMPR TOTAL STREAMS MOUNTPOINT
> /dev/zram0 lz4         248.7M  247M 92.3M 97.4M       2 [SWAP]
> ========================================
>
> I just assumed the message is triggered when the system is really low on
> memory and maybe zram is too slow to provide the memory requested. But
> that's just my layman's assumption :-) For example, today's message was
> emitted during the night:
>
>
> Oct 20 01:26:18 len kernel: [638973.207849] \
>    swap_info_get: Bad swap offset entry 0200f8a7
>
>
> And here are the sysstat numbers for that time frame:
>
>
> $ sar -r -s 00:00 -e 02:00
> Linux 4.13.5-1-ARCH (len)       10/20/2017      _i686_  (2 CPU)
> 12:00:01 AM kbmemfree kbmemused  %memused kbbuffers  kbcached  kbcommit   %commit  kbactive   kbinact   kbdirty
> 12:10:06 AM     70076    948404     93.12         4     19004   1556176     86.58    376608    379408       220
> 12:20:02 AM     80488    937992     92.10         4    180404   1563952     87.01    380184    327736      5568
> 12:30:03 AM     83296    935184     91.82         4    137260   1569776     87.34    329512    330000       280
> 12:40:03 AM     65188    953292     93.60         4     21156   1571048     87.41    386644    389820      1144
> 12:50:03 AM     67512    950968     93.37         4     33452   1570628     87.38    378936    381580      1304
> 01:00:07 AM     65520    952960     93.57         4     24996   1573180     87.53    385396    386152       904
> 01:10:03 AM     66956    951524     93.43         4     35520   1572696     87.50    379548    379364       172
> 01:20:02 AM     67440    951040     93.38         4     88736   1569864     87.34    381764    370472      7080
> 01:30:03 AM     70048    948432     93.12         4     29212   1572504     87.49    383516    381900      1832
> 01:40:04 AM     71532    946948     92.98         4     29220   1570096     87.35    380120    380284      1000
> 01:50:03 AM     65828    952652     93.54         4     34408   1570604     87.38    381040    381028      1604
> Average:        70353    948127     93.09         4     57579   1569139     87.30    376661    371613      1919
>
>
>  == If that is unreadable, here it is again: https://paste.debian.net/991927/
>
>> Is it possible for you to check
>> whether the error exists for normal swap device (not ZRAM)?
>
> I have "normal" (but encrpted) swap configured but with a lower priority:
>
> cat /proc/swaps
> Filename        Type            Size    Used    Priority
> /dev/dm-0       partition       524284  194348  0
> /dev/zram0      partition       254616  253536  32767
>
> I shall disable the zram device and disable encryption too and will report
> back if the message appears again.
>
>> 32bit or 64bit kernel do you use?
>
> I'm using an i686 kernel for this Atom N270 processor (with HT enabled).

Thanks for your information!  I have reproduced your problem.  They
are just false error message.  I will fix that and send out the patch
soon.

Best Regards,
Huang, Ying