Shared memory quantity not being reflected by /proc/meminfo

Shared memory quantity not being reflected by /proc/meminfo

[Allan Duncan]

Since the 2.4.x advent of shm as tmpfs or thereabouts,
/proc/meminfo shows shared memory as 0.  It is in
reality not zero, and is being allocated, and shows
up in /proc/sysvipc/shm and /proc/sys/kernel/shmall
etc..
Neither 2.4.6-pre5 nor 2.4.5-ac17 have the correct
display.

Re: Shared memory quantity not being reflected by /proc/meminfo

[Albert D. Cahalan]

Allan Duncan writes:

> Since the 2.4.x advent of shm as tmpfs or thereabouts,
> /proc/meminfo shows shared memory as 0.  It is in
> reality not zero, and is being allocated, and shows
> up in /proc/sysvipc/shm and /proc/sys/kernel/shmall
> etc..
> Neither 2.4.6-pre5 nor 2.4.5-ac17 have the correct
> display.

You misunderstood what 2.2.xx kernels were reporting.
The "shared" memory in /proc/meminfo refers to something
completely unrelated to SysV shared memory. This is no
longer calculated because the computation was too costly.

Re: Shared memory quantity not being reflected by /proc/meminfo

[Christoph Rohland]

Hi Albert,

On Sat, 23 Jun 2001, Albert D. Cahalan wrote:
> You misunderstood what 2.2.xx kernels were reporting.
> The "shared" memory in /proc/meminfo refers to something
> completely unrelated to SysV shared memory. This is no
> longer calculated because the computation was too costly.

But the load of misinterpretations and the missing value led me to
export the number of shmem pages in later -ac kernels exactly in this
field.

I know it is a change of semantics and because of this both Alan and
me asked for comments if this change is appreciated. I am still
waiting for responses though.

Greetings
		Christoph

Re: Shared memory quantity not being reflected by /proc/meminfo

[Allan Duncan]

OK, it's fine by me if the "shared" under 2.2.x is not the same, however
in that case the field should not appear at all in meminfo, rather than
the current zero value, which leads lesser kernel hackers like me up the
garden path.

Re: Shared memory quantity not being reflected by /proc/meminfo

[Christoph Rohland]

Hi Allan,

On Sun, 24 Jun 2001, Allan Duncan wrote:
> OK, it's fine by me if the "shared" under 2.2.x is not the same,
> however in that case the field should not appear at all in meminfo,
> rather than the current zero value, which leads lesser kernel
> hackers like me up the garden path.

This would probably break a lot of user space apps.

Greetings
		Christoph

Re: Shared memory quantity not being reflected by /proc/meminfo

[Allan Duncan]

Christoph Rohland wrote:
> 
> Hi Allan,
> 
> On Sun, 24 Jun 2001, Allan Duncan wrote:
> > OK, it's fine by me if the "shared" under 2.2.x is not the same,
> > however in that case the field should not appear at all in meminfo,
> > rather than the current zero value, which leads lesser kernel
> > hackers like me up the garden path.
 
> This would probably break a lot of user space apps.


Then only break those that do a lousy parsing of meminfo and change the
heading line to "shared_is_not_real:" or somesuch?
Anyway, aren't the user apps being led up the garden path with the wrong
answer?