lubuntu-qa team mailing list archive

[Leszek Lesner <leszek.lesner@xxxxxx>]

Am 28.09.2013 11:03, schrieb Jörn Schönyan:
> There are freezes with ZRAM in Precise, too. I experience this both
> with original stack/kernel and the enablement stack from Raring.
> Sometimes while shutting down, sometimes after a long session or when
> the RAM is "full". After disabling ZRAM, there are no problems at all.
>
As far as I know the Precise kernel is 3.2 so it should not be affected
by the problem currently introduced by the 3.10.6 kernel. The same goes
for raring which uses the 3.8 kernel. And I hope the ubuntu kernel devs
did not port over the broken zram module from 3.10.6 to the raring kernel.
So there only might be two possibilities:
1. Its another bug.
2. Its not really freezing but just writing a whole lot of chunks to
zram which causes the cpu to run at 100 % for a long time and making
system usage unusable until the chunk is written to zram.

The second thing can happen when lots of memory needs to be compressed
into ram and the cpu is not the fastest (single core for example). So
basically more than 60% of ram needs to be compressed. This takes a
longer time then and maybe halt user input for the time being.
So it would help if you could verify if thats the case for you and if it
still halts when you give it some time to work. (not more than 10 mins
please :) If this is really the case there are ways to limit the ram
that is available for compression (so limit it to 40% for example) or
even tweak the swapping setting to set how big the chunks should be that
are written to swap. (swap in this case made available from zram)
Also in rare occoasions(so if you only have 1 GB RAM and zram only gives
you 250 MB of swapspace and you need more) it might be useful to use
zram in combination with swap space on harddrive. So it would than first
swap out to zram until its full and then write to swap on hd.
As for the shutdown issue this is exactly where it might come to an hold
for some seconds as it needs to clean zram (swap space by zram is
basically unmounted and the contents is written back to ram by swapd or
at least it is trying to write as much as possible back to ram)


>
>
> Am 28.09.2013 01:32, schrieb Phill Whiteside:
>> Hi John,
>>
>> the change in Saucy was that the config was altered so that it was
>> used during the desktop install (Ubiquity), before that it was there
>> just not used for the task of allowing ubiquity to run and install
>> onto a system that we had the crazy situation of the installer
>> needing more RAM than the actual installed system needs.
>>
>> The testing team did many tests to find out just how low we could go
>> with 'desktop installer'. They found ~ 384MB to be the minimum for
>> it. As a server person, I use the alternate installs, but the desktop
>> one is more new comer friendly :)
>>
>> Regards,
>>
>> Phill.
>>
>>
>> On 28 September 2013 00:06, John Hupp <lubuntu@xxxxxxxxxxxxxx
>> <mailto:lubuntu@xxxxxxxxxxxxxx>> wrote:
>>
>>     The news/announcements concerning Saucy tend to say something
>>     "new in Saucy ... zRAM."
>>
>>     But zram-config is installed in my Raring i386 standard desktop
>>     installation, and I didn't install it unless it came along as a
>>     dependency for something.
>>
>>
>>     On 9/27/2013 6:29 PM, Nio Wiklund wrote:
>>
>>         Sorry, I overlooked that John is running Raring. I didn't
>>         think zRAM was
>>         used in Raring, but of course, John can install and run it.
>>         I'm glad you
>>         corrected that mistake by me.
>>
>>         Best regards
>>         Nio
>>
>>         On 2013-09-28 00:08, Phill Whiteside wrote:
>>
>>             hi Nio,
>>
>>             he is running Raring. The bug we see in Saucy on 1227202
>>             is totally
>>             un-related to the sudo parted -l issue.
>>
>>             Getting the race issue sorted out on un-mounting the zram
>>             areas is what
>>             the bug fix is. With all the tests I've done, the
>>
>>               Error: /dev/zram0: unrecognised disk label
>>
>>             Error: /dev/zram1: unrecognised disk label
>>
>>             Has remained until I used the 3.12rc kernel. We will go
>>             battle that
>>             issue on Monday to see if we can find the fix. Also do
>>             read
>>             https://bugs.launchpad.net/ubuntu/+source/linux/+bug/1215379
>>             as we
>>             may be barking up the wrong tree with zram, and should be
>>             using zswap.
>>
>>             Joe cannot tell us which is better to use, just that
>>             zswap was in the
>>             3.11.2 upstream kernel which has been imported into the
>>             latest
>>             3.11.0-9.16 kernel.
>>
>>             It was Unit193 who pointed that issue out, and whilst
>>             getting the race
>>             crash sorted out, it appears that zswap is the updated
>>             system.
>>
>>             Regards,
>>
>>             Phill.
>>
>>
>>             On 27 September 2013 22:54, Nio Wiklund
>>             <nio.wiklund@xxxxxxxxx <mailto:nio.wiklund@xxxxxxxxx>
>>             <mailto:nio.wiklund@xxxxxxxxx
>>             <mailto:nio.wiklund@xxxxxxxxx>>> wrote:
>>
>>                  On 2013-09-27 23:28, John Hupp wrote:
>>                  > On Raring, output from 'sudo parted -l' includes:
>>                  >
>>                  >     Error: /dev/zram0: unrecognised disk label
>>                  >
>>                  > And syslog shows a slew of errors:
>>                  >
>>                  >     Lubuntu kernel: Buffer I/O error on device
>>             zram0, logical
>>                  block 128247
>>                  >
>>                  > Syslog also indicates that half of memory was
>>             given to zram to
>>                  form its
>>                  > block device.
>>                  >
>>                  > Does this mean that half of memory is dedicated to
>>             something that
>>                  isn't
>>                  > working?  And perhaps that machines will hang when
>>             swap is needed?
>>                  >
>>                  > I arrive at this line of questioning because I was
>>             testing an LTSP
>>                  > client using a Lubuntu LTSP server configured with
>>             1 GB, and when
>>                  I drop
>>                  > the client memory configuration to 256 MB, the
>>             *server* has hung on
>>                  > several occasions when I was starting or stopping
>>             Firefox on the
>>                  client
>>                  > (though in one case this coincided with the
>>             startup of a SpiderOak
>>                  > backup operation).   I didn't think of the Magic
>>             SysRq keys at the
>>                  time,
>>                  > and nothing else was responding, so I did hard
>>             shutdowns.
>>                  >
>>                  > I saw a post from Phill Whiteside recently
>>             concerning a rush of
>>                  activity
>>                  > re a zram bug, but it seemed to be directed at Saucy.
>>                  >
>>                  > Are there solutions/workarounds?
>>                  >
>>                  You find a lot of details reading the comments about
>>             this bug.
>>
>>                  https://bugs.launchpad.net/bugs/1227202
>>
>>                  There is a kernel in the pipeline, that we think
>>             will solve most if not
>>                  all of the problems. Until we get the kernel that
>>             can cooperate with
>>                  zRAM, you can switch it off either manually or with
>>             crontab like this:
>>
>>                  guru@Lubuntu-Saucy-b2:~$ sudo crontab -l |tail -n3
>>                  # m h  dom mon dow   command
>>                  @reboot              /sbin/swapoff /dev/zram*
>>                  @reboot              /sbin/rmmod zram
>>
>>                  Best regards
>>                  Nio
>>
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>>
>>
>>
>>             -- 
>>             https://wiki.ubuntu.com/phillw
>>
>>             -- 
>>             https://wiki.ubuntu.com/phillw 
>>
>>
>>
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