Re: [Vserver] vcontext: vc_create_context(): Out of memory

From: Herbert Poetzl <herbert_at_13thfloor.at>
Date: Sat 24 Feb 2007 - 04:05:38 GMT
Message-ID: <20070224040538.GB27632@MAIL.13thfloor.at>

On Fri, Feb 23, 2007 at 07:05:24PM +0900, Taisuke Yamada wrote:
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> Hi.
>
> Yesterday, I tried to find out absolute maximum number of
> virtualhosts I can host on my server, and got this message after
> 40-50VMs:

yes, known issue with the debian kernel, if you
switch to mainline kernels, you will get to
roughly 5000-8000 contexts ...

> # vserver vh2-59 start
> vcontext: vc_create_context(): Out of memory
>
> This is much lower than expected limit (I have 4GB of memory),
> and contrary to above message, there is plenty of free memory:
>
> # free
> total used free shared buffers cached
> Mem: 3633332 2365060 1268272 0 305952 1706888
> -/+ buffers/cache: 352220 3281112
> Swap: 2907724 44 2907680
>
> I also checked ulimit, but all of them are either unlimited or
> huge enough. I did some searching and wondering if vserver is
> limited to 1G (due to 3G/1G split) of memory kernel can use, thus
> ignoring other 3GB.

nope, not at all, though with 4GB memory, the
1G/3G split would be better in most cases, but
again, this issue is not present in mainline
kernels, only in the debian ones ...

> Is this the case? In any case, how can I workaround this issue?

simple, get a 2.6.19.4 and patch it with a
recent patch, e.g. this one:

 http://vserver.13thfloor.at/Experimental/patch-2.6.19.4-vs2.2.0-rc14.diff

and the issue will be gone ... otherwise, wait
for the next debian kernel release, which will
hopefully fix this issue ...

> I'm using Debian GNU/Linux (sid/4.0), with 2.6.18-4-vserver-686
> kernel package. Current environment and vserver status are as follows:
>
> # vserver-stat
> CTX PROC VSZ RSS userTIME sysTIME UPTIME NAME
> 0 54 259.8M 98.8M 10m35s34 2h46m59 1d19h03 root server
> 49294 4 7.7M 2.5M 0m00s00 0m00s20 1m37s30 vh2-10
> 49295 4 7.7M 2.5M 0m00s00 0m00s20 1m36s71 vh2-11
> ...
> 49378 4 7.7M 2.5M 0m00s10 0m00s10 0m06s90 vh2-58

you should really switch to static contexts
too, because the dynamic ones are deprecated
for more than a year now and will go away
soon ...

> # vserver-stat | wc -l
> 51
>
> # vserver-info
> Versions:
> Kernel: 2.6.18-4-vserver-686
> VS-API: 0x00020002
> util-vserver: 0.30.212; Dec 9 2006, 12:26:51
>
> Features:
> CC: gcc, gcc (GCC) 4.1.2 20061115 (prerelease)
> (Debian 4.1.1-20)
> CXX: g++, g++ (GCC) 4.1.2 20061115 (prerelease)
> (Debian 4.1.1-20)
> CPPFLAGS: ''
> CFLAGS: '-Wall -g -O2 -std=c99 -Wall -pedantic -W
> - -funit-at-a-time'
> CXXFLAGS: '-g -O2 -ansi -Wall -pedantic -W
> - -fmessage-length=0 -funit-at-a-time'
> build/host: i486-pc-linux-gnu/i486-pc-linux-gnu

you can probably improve overall performance
of the system, by not compiling for 486
machines too :)

> Use dietlibc: yes
> Build C++ programs: yes
> Build C99 programs: yes
> Available APIs: compat,v11,fscompat,v13,net,v21,oldproc,olduts
> ext2fs Source: e2fsprogs
> syscall(2) invocation: alternative
> vserver(2) syscall#: 273/glibc
>
> Paths:
> prefix: /usr
> sysconf-Directory: /etc
> cfg-Directory: /etc/vservers
> initrd-Directory: $(sysconfdir)/init.d
> pkgstate-Directory: /var/run/vservers
> vserver-Rootdir: /var/lib/vservers
>
> # dmesg
> Linux version 2.6.18-4-vserver-686 (Debian 2.6.18.dfsg.1-10)
> (waldi@debian.org) (gcc version 4.1.2 20061115 (prerelease) (Debian
> 4.1.1-21)) #1 SMP Fri Feb 2 17:58:05 UTC 2007
> ...
> Use a PAE enabled kernel.
> 3200MB HIGHMEM available.
> 896MB LOWMEM available.

a 1G/3G split will give you slightly below
3GB lowmem, and you might consider disabling
highmem completely ... but YMMV

best,
Herbert
 
> Thanks in advance.
> - --
> Taisuke Yamada <tyamadajp_at_spam.rakugaki.org>, http://rakugaki.org/
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