[Crash-utility] [PATCH] add a new command: ipcs

[Dave Anderson]

----- Original Message -----
> Hello Dave,
> 
> I am still locating problems of the SLES9. Until now, nothing was
> found, and I will continue checking the difference. Once I fix them,
> I
> will send the patch. The attachment only fixes the problem of output.
> 
> --
> --
> Regards
> Qiao Nuohan

I see that in all "ipcs -M" displays where there are a number of 
shared memory pages swapped out, it shows something like this:
 
 SHMID_KERNEL     KEY      SHMID      UID   PERMS BYTES      NATTCH STATUS
 ffff810026d75ed0 00000000 360452     3369  600   393216     2      dest 
 PAGES ALLOCATED: 96 RESIDENT: 48 SWAPPED: 36
 SWAP PERFORMANCE ATTEMPTS: 0 SUCCESSES: 0
 VFS_INODE: ffff81003d927d58
 
where on every one of them, the "SWAP PERFORMANCE" values are always zero.

So then I saw that your code just hardwires them to "0L":
 
       fprintf(fp, "PAGES ALLOCATED: %ld RESIDENT: %ld SWAPPED: %ld\n",
               (shm_info.bytes+PAGESIZE()-1) >> PAGESHIFT(),
               shm_info.rss, shm_info.swap);
       fprintf(fp, "SWAP PERFORMANCE ATTEMPTS: %ld SUCCESSES: %ld\n",
               0L, 0L);
       fprintf(fp, "VFS_INODE: %lx\n", shm_info.shm_inode);

And looking at recent kernel sources, Linux stopped using those two 
fields since version 2.6 -- it just returns 0 to the SHM_INFO shmctl
system call.

Here is relevant part of the shmctl(2) man page:

    SHM_INFO (Linux specific)

    Returns  a  shm_info  structure whose fields contain information
    about system resources consumed by shared memory.   This  struc-
    ture  is  defined in <sys/shm.h> if the _GNU_SOURCE feature test
    macro is defined:

      struct shm_info {
          int used_ids;           /* # of currently existing
                                     segments */
          unsigned long shm_tot;  /* Total number of shared
                                     memory pages */
          unsigned long shm_rss;  /* # of resident shared
                                     memory pages */
          unsigned long shm_swp;  /* # of swapped shared
                                     memory pages */
          unsigned long swap_attempts;  /* Unused since Linux 2.4 */
          unsigned long swap_successes; /* Unused since Linux 2.4 */
      };

So that line of output is completely meaningless, and should be
dropped entirely.

That being the case, I'm now thinking that the -M option may be unnecessary? 
The shared memory output could be restricted to just 2 lines:

 SHMID_KERNEL     KEY      SHMID      UID   PERMS BYTES      NATTCH STATUS
 ffff810026d75ed0 00000000 360452     3369  600   393216     2      dest
 PAGES ALLOCATED/RESIDENT/SWAPPED: 96/48/36  VFS_INODE: ffff81003d927d58

Dave