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List:       linux-arm-kernel
Subject:    Re: frustrating slowness !
From:       Benny_Sjöstrand <Benny.Sjostrand () emw ! ericsson ! se>
Date:       2002-07-31 13:30:46
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> On Wed, Jul 31, 2002 at 12:56:24PM +0200, Gad Hayisraeli wrote:
> > Russel: how can i know if my glibc uses shared posix mem ?
> > i use libc-2.2.3 from the arm-linux cross compiler of yours or Erik's (i
> > realy do not remeber) (2.95.3, /usr/local/arm)
>
> I've never really got into posix shared memory stuff, so don't know off
> hand.  However, I'd imagine that if you mount a tmpfs there and its
> not used, then you're not using it.  Conversely, if your application
> works without a /dev/shm directory, then...


"So far I know", I dont believe that glibc use the posix shared
memory internally. The "/dev/shm" only cares on applications that
uses some this functions (in sys/shm.h):
/* Shared memory control operation.  */
extern int shmctl (int __shmid, int __cmd, struct shmid_ds *__buf)
__THROW;

/* Get shared memory segment.  */
extern int shmget (key_t __key, size_t __size, int __shmflg) __THROW;

/* Attach shared memory segment.  */
extern void *shmat (int __shmid, __const void *__shmaddr, int __shmflg)
     __THROW;

/* Detach shared memory segment.  */
extern int shmdt (__const void *__shmaddr) __THROW;

There may be  very few applications that uses this functions, in this
moment I cant even name one application that really depends on this stuff.
Probably course there are better and simpler ways to do IPC ...

I believe that it may work even without the /dev/shm.

/Benny




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