tmpfs size restriction

tmpfs size restriction

[Schwarz,Andre]

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Hi,

I'm facing an issue with tmpfs mounts on PowerPC (mpc83xx specifically).

After "mount -t tmpfs tmpfs /tmp -o size=16m" I can fill the machine's mem
(512MiB) until oom becomes active.

I can't see this on any other machine (x86/ARM) I have access to.
There's always a "no space left on device" message as soon as size specified is
reached ...

kernel versions available are v2.6.26.27 and v2.6.34.7 showing the same
behaviour.

I'd expect the kernel to limit available tmpfs size to 50% of physical memory
anyway.

Any ideas what might be wrong ?


Regards,
André

MATRIX VISION GmbH, Talstrasse 16, DE-71570 Oppenweiler
Registergericht: Amtsgericht Stuttgart, HRB 271090
Geschaeftsfuehrer: Gerhard Thullner, Werner Armingeon, Uwe Furtner


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Re: tmpfs size restriction

[Ira W. Snyder]

On Wed, Apr 20, 2011 at 09:21:00PM +0200, Schwarz,Andre wrote:
> Hi,
> 
> I'm facing an issue with tmpfs mounts on PowerPC (mpc83xx specifically).
> 
> After "mount -t tmpfs tmpfs /tmp -o size=16m" I can fill the machine's mem
> (512MiB) until oom becomes active.
> 
> I can't see this on any other machine (x86/ARM) I have access to.
> There's always a "no space left on device" message as soon as size specified is
> reached ...
> 
> kernel versions available are v2.6.26.27 and v2.6.34.7 showing the same
> behaviour.
> 
> I'd expect the kernel to limit available tmpfs size to 50% of physical memory
> anyway.
> 
> Any ideas what might be wrong ?
> 

For what it is worth, I tried this on an 8349EA board, using 2.6.38rc8.
It behaved exactly as I would expect. A short log is below. Maybe your
mount command parses options differently on the powerpc machine? Try it
with the mount options before the mount points?

iws@carmaboard7 ~ $ mkdir mnt
mkdir: cannot create directory `mnt': File exists
iws@carmaboard7 ~ $ ls mnt/
iws@carmaboard7 ~ $ sudo mount -t tmpfs -o size=16m,users none mnt
iws@carmaboard7 ~ $ ls mnt/
iws@carmaboard7 ~ $ mount | grep mnt
none on /home/iws/mnt type tmpfs (rw,nosuid,nodev,noexec,relatime,size=16384k)
iws@carmaboard7 ~ $ cd ^C
iws@carmaboard7 ~ $ dd if=/dev/zero of=mnt/file.bin bs=1M count=18
dd: writing `mnt/file.bin': No space left on device
16+0 records in
15+0 records out
16760832 bytes (17 MB) copied, 0.313836 s, 53.4 MB/s
iws@carmaboard7 ~ $ du -b mnt/file.bin 
16760832        mnt/file.bin
iws@carmaboard7 ~ $ df -h mnt
Filesystem            Size  Used Avail Use% Mounted on
none                   16M     -     -   -  /home/iws/mnt
iws@carmaboard7 ~ $ uname -a
Linux carmaboard7.correlator.pvt 2.6.38-rc8-00028-g24d6894 #1 Tue Mar 8 09:48:15 PST 2011 ppc e300c1 GNU/Linux
iws@carmaboard7 ~ $ cat /proc/cpuinfo 
processor       : 0
cpu             : e300c1
clock           : 533.333328MHz
revision        : 3.1 (pvr 8083 0031)
bogomips        : 133.29
timebase        : 66646782
platform        : MPC834x MDS
model           : CARMA
Memory          : 256 MB

Hope it helps,
Ira

Re: tmpfs size restriction

[Schwarz,Andre]

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"Ira W. Snyder" <iws@ovro.caltech.edu> hat am 20. April 2011 um 22:44
geschrieben:

> On Wed, Apr 20, 2011 at 09:21:00PM +0200, Schwarz,Andre wrote:
> > Hi,
> >
> > I'm facing an issue with tmpfs mounts on PowerPC (mpc83xx specifically).
> >
> > After "mount -t tmpfs tmpfs /tmp -o size=16m" I can fill the machine's mem
> > (512MiB) until oom becomes active.
> >
> > I can't see this on any other machine (x86/ARM) I have access to.
> > There's always a "no space left on device" message as soon as size specified
> > is
> > reached ...
> >
> > kernel versions available are v2.6.26.27 and v2.6.34.7 showing the same
> > behaviour.
> >
> > I'd expect the kernel to limit available tmpfs size to 50% of physical
> > memory
> > anyway.
> >
> > Any ideas what might be wrong ?
> >
>
> For what it is worth, I tried this on an 8349EA board, using 2.6.38rc8.
> It behaved exactly as I would expect. A short log is below. Maybe your
> mount command parses options differently on the powerpc machine? 
even with incorrect/missing mount options the kernel should limit the size
to 50% phys mem ... at least according to doc/tmpfs.txt 
 

> Try it with the mount options before the mount points? 
no effect.
 

>
> iws@carmaboard7 ~ $ mkdir mnt
> mkdir: cannot create directory `mnt': File exists
> iws@carmaboard7 ~ $ ls mnt/
> iws@carmaboard7 ~ $ sudo mount -t tmpfs -o size=16m,users none mnt
> iws@carmaboard7 ~ $ ls mnt/
> iws@carmaboard7 ~ $ mount | grep mnt
> none on /home/iws/mnt type tmpfs (rw,nosuid,nodev,noexec,relatime,size=16384k)
> iws@carmaboard7 ~ $ cd ^C
> iws@carmaboard7 ~ $ dd if=/dev/zero of=mnt/file.bin bs=1M count=18
> dd: writing `mnt/file.bin': No space left on device
> 16+0 records in
> 15+0 records out
> 16760832 bytes (17 MB) copied, 0.313836 s, 53.4 MB/s
> iws@carmaboard7 ~ $ du -b mnt/file.bin
> 16760832        mnt/file.bin
> iws@carmaboard7 ~ $ df -h mnt
> Filesystem            Size  Used Avail Use% Mounted on
> none                   16M     -     -   -  /home/iws/mnt
> iws@carmaboard7 ~ $ uname -a
> Linux carmaboard7.correlator.pvt 2.6.38-rc8-00028-g24d6894 #1 Tue Mar 8
> 09:48:15 PST 2011 ppc e300c1 GNU/Linux
> iws@carmaboard7 ~ $ cat /proc/cpuinfo
> processor       : 0
> cpu             : e300c1
> clock           : 533.333328MHz
> revision        : 3.1 (pvr 8083 0031)
> bogomips        : 133.29
> timebase        : 66646782
> platform        : MPC834x MDS
> model           : CARMA
> Memory          : 256 MB 
yes - this is the expected behaviour I can see on all systems ... except mine
:-( 
 

> > Hope it helps, 
no - but thank you for trying. 
 

Cheers,André 

MATRIX VISION GmbH, Talstrasse 16, DE-71570 Oppenweiler
Registergericht: Amtsgericht Stuttgart, HRB 271090
Geschaeftsfuehrer: Gerhard Thullner, Werner Armingeon, Uwe Furtner


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