Re: swap_info_get: Bad swap offset entry 0200f8a7
From: Christian Kujau
Date: Fri Oct 20 2017 - 21:07:50 EST
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 response,
Christian.
--
BOFH excuse #403:
Sysadmin didn't hear pager go off due to loud music from bar-room speakers.