SHM Not working in 2.4.0-prerelease

SHM Not working in 2.4.0-prerelease

[Shawn Starr]

I have created the shm directory in /dev

drwxrwxrwt   1 root     root            0 Jan  3 09:51 shm/

in my fstab i have:

shmfs /dev/shm shm defaults 0 0


when I display with top:


Mem:    62496K av,   61248K used,    1248K free,       0K shrd,    1868K
buff
Swap:   64252K av,   20016K used,   44236K free                   27900K
cached

[spstarr@coredump /etc]$ free
             total       used       free     shared    buffers
cached
Mem:         62496      61264       1232          0       1248
28848


There's no shared memory being used?

mount
...
shmfs on /dev/shm type shm (rw)

the shmfs is mounted. Is there any configuration i need to get shm
memory activiated?

Thanks,

Shawn Starr.

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Re: SHM Not working in 2.4.0-prerelease

[Doug McNaught]

Shawn Starr <shawn.starr@home.net> writes:

> [spstarr@coredump /etc]$ free
>              total       used       free     shared    buffers
> cached
> Mem:         62496      61264       1232          0       1248
> 28848
> 
> 
> There's no shared memory being used?

[...]

> the shmfs is mounted. Is there any configuration i need to get shm
> memory activiated?

The 'shared' field in /proc/meminfo (source for 'top' and 'free') has
nothing to do with {SysV,POSIX} shared memory.  The 'shared' field
referred to memory that was used by more than one process (shared
libraries, shared text segments etc).  As I understand it, under 2.4
the 'shared' field is very expensive to calculate, so we don't--the
zero value is there to avoid breaking programs that parse
/proc/meminfo. 

-Doug
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Re: SHM Not working in 2.4.0-prerelease

[Albert D. Cahalan]

>> [spstarr@coredump /etc]$ free
>>              total       used       free     shared    buffers
...
>> the shmfs is mounted. Is there any configuration i need to get
>> shm memory activiated?
>
> The 'shared' field in /proc/meminfo (source for 'top' and 'free')
> has nothing to do with {SysV,POSIX} shared memory.

Hey, that would be a good use for the field.
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Re: SHM Not working in 2.4.0-prerelease

[Shawn Starr]

ahh ok, so everythings fine then. It would be nice though to see that
value perhaps in future they'll be a way.

Thanks,

Shawn.

Doug McNaught wrote:

> Shawn Starr <shawn.starr@home.net> writes:
>
> > [spstarr@coredump /etc]$ free
> >              total       used       free     shared    buffers
> > cached
> > Mem:         62496      61264       1232          0       1248
> > 28848
> >
> >
> > There's no shared memory being used?
>
> [...]
>
> > the shmfs is mounted. Is there any configuration i need to get shm
> > memory activiated?
>
> The 'shared' field in /proc/meminfo (source for 'top' and 'free') has
> nothing to do with {SysV,POSIX} shared memory.  The 'shared' field
> referred to memory that was used by more than one process (shared
> libraries, shared text segments etc).  As I understand it, under 2.4
> the 'shared' field is very expensive to calculate, so we don't--the
> zero value is there to avoid breaking programs that parse
> /proc/meminfo.
>
> -Doug

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Re: SHM Not working in 2.4.0-prerelease

[Christoph Rohland]

"Albert D. Cahalan" <acahalan@cs.uml.edu> writes:

> >> [spstarr@coredump /etc]$ free
> >>              total       used       free     shared    buffers
> ...
> >> the shmfs is mounted. Is there any configuration i need to get
> >> shm memory activiated?
> >
> > The 'shared' field in /proc/meminfo (source for 'top' and 'free')
> > has nothing to do with {SysV,POSIX} shared memory.
> 
> Hey, that would be a good use for the field.

Not a bad idea. Then we could tell free etc to subtract this from the
+/- cached free numbers...

I will look into this.

        Christoph

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