cgroup memory limit problems

cgroup memory limit problems

[Arkadiusz Miśkiewicz]

Hi,

I have a machine with 6GB of ram and a cgroup for apache processes limited to 
                memory.limit_in_bytes = "5100M";
                memory.soft_limit_in_bytes = "5000M";

Unfortunately when apache processes ate all ram assigned to their cgroup load 
on whole machine jumps the roof.

cgroup aware OOM kicks in, kills one process and that doesn't help.

If I'm fast enough I notice and then apache processes require tons of kill -9 
(I'm doing "killall -9 apache" in a while (true) loop for 20-30s) to get 
killed (and that not always succeeds - sometimes I'm unable to kill these and 
I'm just doing sysrq u, s, b after few minutes.. if I'm lucky. Sometimes I 
cannot do any command).

This all happens on 2.6.38.8 kernel.
http://ixion.pld-linux.org/~arekm/cgroup-eaten-memory-failure-1.txt
for kernel log. It ends with reboot of the machine.

Now the question is - is this is how cgroup memory limit supposed to work? If 
yes then it's hardly usable but maybe there are some patches for this?

Would newer kernels be better ? (cannot test immediately since newer kernels 
kill ipmi connectivity on that machine). I would expect apache processes to be 
killed without taking down entire machine.

ps. found similar history at http://serverfault.com/questions/211509/how-to-
stop-apache-from-crashing-my-entire-server from year ago
-- 
Arkadiusz Miśkiewicz        PLD/Linux Team
arekm / maven.pl            http://ftp.pld-linux.org/
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Re: cgroup memory limit problems

[Daniel Lezcano]

On 11/09/2011 09:57 PM, Arkadiusz Miśkiewicz wrote:
> Hi,
>
> I have a machine with 6GB of ram and a cgroup for apache processes limited to 
>                 memory.limit_in_bytes = "5100M";
>                 memory.soft_limit_in_bytes = "5000M";
>
> Unfortunately when apache processes ate all ram assigned to their cgroup load 
> on whole machine jumps the roof.
>
> cgroup aware OOM kicks in, kills one process and that doesn't help.

Did you try to disable the oom with the "memory.oom_control" file by
setting it to "1" ?

If the cgroup runs out of memory they should be stopped until you give
more memory or kill some tasks.

Hope that helps
  -- Daniel

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Re: cgroup memory limit problems

[Arkadiusz Miśkiewicz]

On Wednesday 09 of November 2011, Daniel Lezcano wrote:
> On 11/09/2011 09:57 PM, Arkadiusz Miśkiewicz wrote:
> > Hi,
> > 
> > I have a machine with 6GB of ram and a cgroup for apache processes
> > limited to
> > 
> >                 memory.limit_in_bytes = "5100M";
> >                 memory.soft_limit_in_bytes = "5000M";
> > 
> > Unfortunately when apache processes ate all ram assigned to their cgroup
> > load on whole machine jumps the roof.
> > 
> > cgroup aware OOM kicks in, kills one process and that doesn't help.
> 
> Did you try to disable the oom with the "memory.oom_control" file by
> setting it to "1" ?

No, will try.

> 
> If the cgroup runs out of memory they should be stopped until you give
> more memory or kill some tasks.

I hope these tasks will be allowed to be killed when oom will be disabled. 
Right now it's often impossible to kill these.

Anyway I would preffer httpd processed to be automaticly killed without manual 
intervention. 

> Hope that helps
>   -- Daniel


-- 
Arkadiusz Miśkiewicz        PLD/Linux Team
arekm / maven.pl            http://ftp.pld-linux.org/
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Re: cgroup memory limit problems

[Balbir Singh]

2011/11/10 Arkadiusz Miśkiewicz <arekm@maven.pl>:
>
> Hi,
>
> I have a machine with 6GB of ram and a cgroup for apache processes limited to
>                memory.limit_in_bytes = "5100M";
>                memory.soft_limit_in_bytes = "5000M";
>

Can you please send the output of memory.stat?

> Unfortunately when apache processes ate all ram assigned to their cgroup load
> on whole machine jumps the roof.
>
> cgroup aware OOM kicks in, kills one process and that doesn't help.
>
> If I'm fast enough I notice and then apache processes require tons of kill -9
> (I'm doing "killall -9 apache" in a while (true) loop for 20-30s) to get
> killed (and that not always succeeds - sometimes I'm unable to kill these and
> I'm just doing sysrq u, s, b after few minutes.. if I'm lucky. Sometimes I
> cannot do any command).
>
> This all happens on 2.6.38.8 kernel.
> http://ixion.pld-linux.org/~arekm/cgroup-eaten-memory-failure-1.txt
> for kernel log. It ends with reboot of the machine.
>

From the logs

"Nov  9 20:48:53 tm2 kernel: [18300.349106] Task in /somecgroup/httpd
killed as a result of limit of /somecgroup/httpd
Nov  9 20:48:53 tm2 kernel: [18300.349110] memory: usage 5222400kB,
limit 5222400kB, failcnt 282869
Nov  9 20:48:53 tm2 kernel: [18300.349113] memory+swap: usage 0kB,
limit 9007199254740991kB, failcnt 0"

It seems like you've disabled swap, is that correct?

Balbir
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Re: cgroup memory limit problems

[Balbir Singh]

CC'ing cgroups list

Balbir

2011/11/10 Balbir Singh <bsingharora@gmail.com>:
> 2011/11/10 Arkadiusz Miśkiewicz <arekm@maven.pl>:
>>
>> Hi,
>>
>> I have a machine with 6GB of ram and a cgroup for apache processes limited to
>>                memory.limit_in_bytes = "5100M";
>>                memory.soft_limit_in_bytes = "5000M";
>>
>
> Can you please send the output of memory.stat?
>
>> Unfortunately when apache processes ate all ram assigned to their cgroup load
>> on whole machine jumps the roof.
>>
>> cgroup aware OOM kicks in, kills one process and that doesn't help.
>>
>> If I'm fast enough I notice and then apache processes require tons of kill -9
>> (I'm doing "killall -9 apache" in a while (true) loop for 20-30s) to get
>> killed (and that not always succeeds - sometimes I'm unable to kill these and
>> I'm just doing sysrq u, s, b after few minutes.. if I'm lucky. Sometimes I
>> cannot do any command).
>>
>> This all happens on 2.6.38.8 kernel.
>> http://ixion.pld-linux.org/~arekm/cgroup-eaten-memory-failure-1.txt
>> for kernel log. It ends with reboot of the machine.
>>
>
> From the logs
>
> "Nov  9 20:48:53 tm2 kernel: [18300.349106] Task in /somecgroup/httpd
> killed as a result of limit of /somecgroup/httpd
> Nov  9 20:48:53 tm2 kernel: [18300.349110] memory: usage 5222400kB,
> limit 5222400kB, failcnt 282869
> Nov  9 20:48:53 tm2 kernel: [18300.349113] memory+swap: usage 0kB,
> limit 9007199254740991kB, failcnt 0"
>
> It seems like you've disabled swap, is that correct?
>
> Balbir
>
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Re: cgroup memory limit problems

[Arkadiusz Miśkiewicz]

On Wednesday 09 of November 2011, Balbir Singh wrote:
> 2011/11/10 Arkadiusz Miśkiewicz <arekm@maven.pl>:
> > Hi,
> > 
> > I have a machine with 6GB of ram and a cgroup for apache processes
> > limited to memory.limit_in_bytes = "5100M";
> >                memory.soft_limit_in_bytes = "5000M";
> 
> Can you please send the output of memory.stat?

Right now there is small number of users using this server (night here) so:

# cat /dev/cgroup/memory/somecgroup/httpd/memory.stat
cache 511426560
rss 2637795328
mapped_file 2129920
pgpgin 32233755
pgpgout 31509870
inactive_anon 720896
active_anon 2637271040
inactive_file 255959040
active_file 255234048
unevictable 0
hierarchical_memory_limit 5347737600
total_cache 511426560
total_rss 2637795328
total_mapped_file 2129920
total_pgpgin 32233755
total_pgpgout 31509870
total_inactive_anon 720896
total_active_anon 2637271040
total_inactive_file 255959040
total_active_file 255234048
total_unevictable 0

> 
> > Unfortunately when apache processes ate all ram assigned to their cgroup
> > load on whole machine jumps the roof.
> > 
> > cgroup aware OOM kicks in, kills one process and that doesn't help.
> > 
> > If I'm fast enough I notice and then apache processes require tons of
> > kill -9 (I'm doing "killall -9 apache" in a while (true) loop for
> > 20-30s) to get killed (and that not always succeeds - sometimes I'm
> > unable to kill these and I'm just doing sysrq u, s, b after few
> > minutes.. if I'm lucky. Sometimes I cannot do any command).
> > 
> > This all happens on 2.6.38.8 kernel.
> > http://ixion.pld-linux.org/~arekm/cgroup-eaten-memory-failure-1.txt
> > for kernel log. It ends with reboot of the machine.
> 
> From the logs
> 
> "Nov  9 20:48:53 tm2 kernel: [18300.349106] Task in /somecgroup/httpd
> killed as a result of limit of /somecgroup/httpd
> Nov  9 20:48:53 tm2 kernel: [18300.349110] memory: usage 5222400kB,
> limit 5222400kB, failcnt 282869
> Nov  9 20:48:53 tm2 kernel: [18300.349113] memory+swap: usage 0kB,
> limit 9007199254740991kB, failcnt 0"
> 
> It seems like you've disabled swap, is that correct?

Yes, this machine has no swap but the kernel has 

# zcat /proc/config.gz |grep CGROUP_MEM
CONFIG_CGROUP_MEM_RES_CTLR=y
CONFIG_CGROUP_MEM_RES_CTLR_SWAP=y
# CONFIG_CGROUP_MEM_RES_CTLR_SWAP_ENABLED is not set

+ ctlr swap wasn't enabled at boot.

> Balbir

ps. vger.kernel.org doesn't like my address (no idea why and postmaster@ is 
silent), so likely my reply won't reach cgroup@
-- 
Arkadiusz Miśkiewicz        PLD/Linux Team
arekm / maven.pl            http://ftp.pld-linux.org/
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Re: cgroup memory limit problems

[KAMEZAWA Hiroyuki]

On Wed, 9 Nov 2011 23:58:57 +0100
Arkadiusz Miśkiewicz <arekm@maven.pl> wrote:

> On Wednesday 09 of November 2011, Balbir Singh wrote:
> > 2011/11/10 Arkadiusz Miśkiewicz <arekm@maven.pl>:
> > > Hi,
> > > 
> > > I have a machine with 6GB of ram and a cgroup for apache processes
> > > limited to memory.limit_in_bytes = "5100M";
> > >                memory.soft_limit_in_bytes = "5000M";
> > 
> > Can you please send the output of memory.stat?
> 
> Right now there is small number of users using this server (night here) so:
> 
> # cat /dev/cgroup/memory/somecgroup/httpd/memory.stat
> cache 511426560
> rss 2637795328
> mapped_file 2129920
> pgpgin 32233755
> pgpgout 31509870
> inactive_anon 720896
> active_anon 2637271040
> inactive_file 255959040
> active_file 255234048
> unevictable 0
> hierarchical_memory_limit 5347737600
> total_cache 511426560
> total_rss 2637795328
> total_mapped_file 2129920
> total_pgpgin 32233755
> total_pgpgout 31509870
> total_inactive_anon 720896
> total_active_anon 2637271040
> total_inactive_file 255959040
> total_active_file 255234048
> total_unevictable 0
> 
> > 
> > > Unfortunately when apache processes ate all ram assigned to their cgroup
> > > load on whole machine jumps the roof.
> > > 
> > > cgroup aware OOM kicks in, kills one process and that doesn't help.
> > > 
> > > If I'm fast enough I notice and then apache processes require tons of
> > > kill -9 (I'm doing "killall -9 apache" in a while (true) loop for
> > > 20-30s) to get killed (and that not always succeeds - sometimes I'm
> > > unable to kill these and I'm just doing sysrq u, s, b after few
> > > minutes.. if I'm lucky. Sometimes I cannot do any command).
> > > 
> > > This all happens on 2.6.38.8 kernel.
> > > http://ixion.pld-linux.org/~arekm/cgroup-eaten-memory-failure-1.txt
> > > for kernel log. It ends with reboot of the machine.
> > 
> > From the logs
> > 
> > "Nov  9 20:48:53 tm2 kernel: [18300.349106] Task in /somecgroup/httpd
> > killed as a result of limit of /somecgroup/httpd
> > Nov  9 20:48:53 tm2 kernel: [18300.349110] memory: usage 5222400kB,
> > limit 5222400kB, failcnt 282869
> > Nov  9 20:48:53 tm2 kernel: [18300.349113] memory+swap: usage 0kB,
> > limit 9007199254740991kB, failcnt 0"
> > 
> > It seems like you've disabled swap, is that correct?
> 
> Yes, this machine has no swap but the kernel has 
> 
> # zcat /proc/config.gz |grep CGROUP_MEM
> CONFIG_CGROUP_MEM_RES_CTLR=y
> CONFIG_CGROUP_MEM_RES_CTLR_SWAP=y
> # CONFIG_CGROUP_MEM_RES_CTLR_SWAP_ENABLED is not set
> 
> + ctlr swap wasn't enabled at boot.
> 
> > Balbir
> 
> ps. vger.kernel.org doesn't like my address (no idea why and postmaster@ is 
> silent), so likely my reply won't reach cgroup@

If you can, please try the latest kernels.

recent 2 commits

commit 79dfdaccd1d5b40ff7cf4a35a0e63696ebb78b4d
" memcg: make oom_lock 0 and 1 based rather than counter "
commit 1d65f86db14806cf7b1218c7b4ecb8b4db5af27d
"  mm: preallocate page before lock_page() at filemap COW"

are works well against fork-bomb under memcg. In my test, make -j under
swapless memcg hangs (or takes long time) to be oom-killed.

Thanks,
-Kame






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Re: cgroup memory limit problems

[Michal Hocko]

Sorry to reply late

On Thu 10-11-11 09:10:12, KAMEZAWA Hiroyuki wrote:
> On Wed, 9 Nov 2011 23:58:57 +0100
[...]
> If you can, please try the latest kernels.
> 
> recent 2 commits
> 
> commit 79dfdaccd1d5b40ff7cf4a35a0e63696ebb78b4d
> " memcg: make oom_lock 0 and 1 based rather than counter "

This one needs a follow up fix (23751be0094012eb6b4756fa80ca54b3eb83069f
"memcg: fix hierarchical oom locking")

> commit 1d65f86db14806cf7b1218c7b4ecb8b4db5af27d
> "  mm: preallocate page before lock_page() at filemap COW"
> 
> are works well against fork-bomb under memcg. In my test, make -j under
> swapless memcg hangs (or takes long time) to be oom-killed.

-- 
Michal Hocko
SUSE Labs
SUSE LINUX s.r.o.
Lihovarska 1060/12
190 00 Praha 9    
Czech Republic