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why /dev/shm is not used

This is a discussion on why /dev/shm is not used within the Linux Operating System forums, part of the Unix Operating Systems category; --> hi so my quastion is why /dev/shm is never used on my system? or mayby it's used but I ...


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  #1 (permalink)  
Old 01-18-2008, 08:46 AM
serwerr@gmail.com
 
Posts: n/a
Default why /dev/shm is not used

hi

so my quastion is why /dev/shm is never used on my system?
or mayby it's used but I can't see it?


#df -h

Filesystem Size Used Avail Use% Mounted on
/dev/hda2 25G 24G 1.8G 94% /
/dev/hda1 13G 13G 86M 100% /mnt/xp
none 379M 0 379M 0% /dev/shm


#mount
/dev/hda2 on / type reiserfs (rw,noatime)
none on /dev type devfs (rw)
none on /proc type proc (rw)
none on /sys type sysfs (rw)
none on /dev/pts type devpts (rw)
/dev/hda1 on /mnt/xp type ntfs (ro,noexec,nosuid,nodev,umask=022)
none on /dev/shm type tmpfs (rw,noexec,nosuid,nodev)
none on /proc/bus/usb type usbfs (rw)

my machine is:
AMD ATHLON XP 2200+ ( 1.8 GHz )
K7VZA PCB 3.0 AGP 4x
3x 256 MB RAM - DIMM 133MHz
ATI RADEON 9200SE 128 MB RAM 64bit

my distibiution is gentoo,
kernel is 2.6.11-r6
xorg 6.8.2-r1
ati-drivers 8.12.10
kde-3.3.2

hardware 3d acceleration runs fine, with quake3 I get more fps than on
windows

but my system is so sloooow
after lets say 3 hours of work it takes more than 10secs to open new
tab in firefox.

it looks for me like the system is using only 10% ram or something I
guess

anyway what should by the right size of /dev/shm ?

thanks
serwerr

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  #2 (permalink)  
Old 01-18-2008, 08:47 AM
Thorn
 
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Default Re: why /dev/shm is not used

On 10 Jun 2005 01:28:21 -0700, serwerr@gmail.com Cried: Read These Runes!:
> hi
>
> so my quastion is why /dev/shm is never used on my system?
> or mayby it's used but I can't see it?
>
>
> #df -h
>
> Filesystem Size Used Avail Use% Mounted on
> /dev/hda2 25G 24G 1.8G 94% /
> /dev/hda1 13G 13G 86M 100% /mnt/xp
> none 379M 0 379M 0% /dev/shm

^^^^^^^^

Is "none" a valid filesystem? Try changing that to tmpfs and see what
happens.

Thorn
--
Your lucky number is 3552664958674928. Watch for it everywhere.
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  #3 (permalink)  
Old 01-18-2008, 08:47 AM
Daniel Ganek
 
Posts: n/a
Default Re: why /dev/shm is not used

serwerr@gmail.com wrote:
> hi
>
> so my quastion is why /dev/shm is never used on my system?
> or mayby it's used but I can't see it?
>
>
> #df -h
>
> Filesystem Size Used Avail Use% Mounted on
> /dev/hda2 25G 24G 1.8G 94% /
> /dev/hda1 13G 13G 86M 100% /mnt/xp
> none 379M 0 379M 0% /dev/shm
>
>
> #mount
> /dev/hda2 on / type reiserfs (rw,noatime)
> none on /dev type devfs (rw)
> none on /proc type proc (rw)
> none on /sys type sysfs (rw)
> none on /dev/pts type devpts (rw)
> /dev/hda1 on /mnt/xp type ntfs (ro,noexec,nosuid,nodev,umask=022)
> none on /dev/shm type tmpfs (rw,noexec,nosuid,nodev)
> none on /proc/bus/usb type usbfs (rw)
>
> my machine is:
> AMD ATHLON XP 2200+ ( 1.8 GHz )
> K7VZA PCB 3.0 AGP 4x
> 3x 256 MB RAM - DIMM 133MHz
> ATI RADEON 9200SE 128 MB RAM 64bit
>
> my distibiution is gentoo,
> kernel is 2.6.11-r6
> xorg 6.8.2-r1
> ati-drivers 8.12.10
> kde-3.3.2
>
> hardware 3d acceleration runs fine, with quake3 I get more fps than on
> windows
>
> but my system is so sloooow
> after lets say 3 hours of work it takes more than 10secs to open new
> tab in firefox.
>
> it looks for me like the system is using only 10% ram or something I
> guess
>
> anyway what should by the right size of /dev/shm ?
>
> thanks
> serwerr
>


Shared memory is used by cooperating applications - If you're not running any such apps
then it's not used or needed. Don't worry about unless some app complains that it can't
allocate enough shared memory.

If the system is only using 10% of ram then it only needs 10%. firefox is slow because of
something other than memory.

/dan
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  #4 (permalink)  
Old 01-18-2008, 08:47 AM
serwerr
 
Posts: n/a
Default Re: why /dev/shm is not used

I'm using ATI's binary driver which needs to have /dev/shm.

>firefox is slow because of something other than memory.


could you recommend me any tool/method to investigate this issue?

it's not only firefox problem. it's any application problem.

even quake3 and BillardGL are very slow after my machine is running for
couple of hours.

thanks

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  #5 (permalink)  
Old 01-18-2008, 08:47 AM
Andreas Janssen
 
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Default Re: why /dev/shm is not used

Hello

Thorn (<Raptor@Etruscan.Warrior>) wrote:
> On 10 Jun 2005 01:28:21 -0700, serwerr@gmail.com Cried: Read These
> Runes!:
>> so my quastion is why /dev/shm is never used on my system?
>> or mayby it's used but I can't see it?
>>
>>
>> #df -h
>>
>> Filesystem Size Used Avail Use% Mounted on
>> /dev/hda2 25G 24G 1.8G 94% /
>> /dev/hda1 13G 13G 86M 100% /mnt/xp
>> none 379M 0 379M 0% /dev/shm

> ^^^^^^^^
>
> Is "none" a valid filesystem? Try changing that to tmpfs and see what
> happens.


No, but that is not the file system, it is the device file. And because
tmpfs is a virtual file system, it doesn't habe one. Same like proc,
sys, usbdevfs and all the other virtual file systems.

best regards
Andreas Janssen

--
Andreas Janssen <andreas.janssen@bigfoot.com>
PGP-Key-ID: 0xDC801674 ICQ #17079270
Registered Linux User #267976
http://www.andreas-janssen.de/debian-tipps-sarge.html
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  #6 (permalink)  
Old 01-18-2008, 08:47 AM
Jean-David Beyer
 
Posts: n/a
Default Re: why /dev/shm is not used

Andreas Janssen wrote:
> Hello
>
> Thorn (<Raptor@Etruscan.Warrior>) wrote:
>
>>On 10 Jun 2005 01:28:21 -0700, serwerr@gmail.com Cried: Read These
>>Runes!:
>>
>>>so my quastion is why /dev/shm is never used on my system?
>>>or mayby it's used but I can't see it?
>>>
>>>
>>>#df -h
>>>
>>>Filesystem Size Used Avail Use% Mounted on
>>>/dev/hda2 25G 24G 1.8G 94% /
>>>/dev/hda1 13G 13G 86M 100% /mnt/xp
>>>none 379M 0 379M 0% /dev/shm

>>
>>^^^^^^^^
>>
>>Is "none" a valid filesystem? Try changing that to tmpfs and see what
>>happens.

>
>
> No, but that is not the file system, it is the device file. And because
> tmpfs is a virtual file system, it doesn't habe one. Same like proc,
> sys, usbdevfs and all the other virtual file systems.
>
> best regards
> Andreas Janssen
>

Here is what my /etc/fstab looks like (boring lines deleted).

none /dev/shm tmpfs defaults 0 0


--
.~. Jean-David Beyer Registered Linux User 85642.
/V\ PGP-Key: 9A2FC99A Registered Machine 241939.
/( )\ Shrewsbury, New Jersey http://counter.li.org
^^-^^ 17:25:00 up 13 days, 1 min, 3 users, load average: 4.28, 4.31, 4.20
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  #7 (permalink)  
Old 01-18-2008, 08:47 AM
Robert Nichols
 
Posts: n/a
Default Re: why /dev/shm is not used

In article <1118417261.431933.320910@g43g2000cwa.googlegroups .com>,
serwerr <serwerr@gmail.com> wrote:
:I'm using ATI's binary driver which needs to have /dev/shm.
:
:>firefox is slow because of something other than memory.
:
:could you recommend me any tool/method to investigate this issue?
:
:it's not only firefox problem. it's any application problem.
:
:even quake3 and BillardGL are very slow after my machine is running for
:couple of hours.

What memory usage does "free" actually report? I've seen nothing more
than your guess that you are using only a small portion of your memory.

--
Bob Nichols AT comcast.net I am "rnichols42"
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  #8 (permalink)  
Old 01-18-2008, 08:47 AM
serwerr
 
Posts: n/a
Default Re: why /dev/shm is not used

from X.org with Gnome and Firefox running

root#free
total used free shared buffers
cached
Mem: 775652 188124 587528 0 8028
92740
-/+ buffers/cache: 87356 688296
Swap: 0 0 0

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  #9 (permalink)  
Old 01-18-2008, 08:48 AM
Thorn
 
Posts: n/a
Default Re: why /dev/shm is not used

On Fri, 10 Jun 2005 17:28:47 -0400, Jean-David Beyer Cried: Read These Runes!:
> Andreas Janssen wrote:

----
>> No, but that is not the file system, it is the device file. And because
>> tmpfs is a virtual file system, it doesn't habe one. Same like proc,
>> sys, usbdevfs and all the other virtual file systems.

---
> Here is what my /etc/fstab looks like (boring lines deleted).
>
> none /dev/shm tmpfs defaults 0 0


Confused. I build tmpfs and proc file support into my kernels. Proc
provides some nice info and tmpfs is required for POSIX compliance; at least
per my ATI Radeon binary install instructions.

proc /proc proc defaults 0 0
tmpfs /dev/shm tmpfs defaults 0 0

although:

~$ du /dev/shm
0 /dev/shm

and:

~$ df -h | grep shm
tmpfs 505M 0 505M 0% /dev/shm

Thorn
--
God is a comic playing to an audience that's afraid to laugh.
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  #10 (permalink)  
Old 01-18-2008, 08:48 AM
Robert Nichols
 
Posts: n/a
Default Re: why /dev/shm is not used

In article <1118479457.548534.170560@z14g2000cwz.googlegroups .com>,
serwerr <serwerr@gmail.com> wrote:
:from X.org with Gnome and Firefox running
:
:root#free
: total used free shared buffers cached
:Mem: 775652 188124 587528 0 8028 92740
:-/+ buffers/cache: 87356 688296
:Swap: 0 0 0

Presumably that was taken while the system was slow.

OK, I'm perplexed. The amount of unused memory (587528) is unusually
large. A system that's been active for a while would normally show much
more memory in the "cached" category. The only time I see numbers
similar to what you show is when a very large process has just
terminated, freeing its memory.

Does "top" show anything unusual going on? Is there a lot of disk
activity? It could be that all you're seeing is anacron running all the
stuff in /etc/cron.daily because the system wasn't up during the wee
hours of the morning when those jobs would normally be scheduled.
If the problem begins 1 hour after booting, that's the most likely
cause.

A final thought: Have you checked your system for a possible rootkit?

--
Bob Nichols AT comcast.net I am "rnichols42"
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