Overview:

pipcs gives an "ipcs -u"-level overview of POSIX and System V shared memory.  For now, it shows page count/residency as well as totals.  Eventually I'll add information regarding POSIX semaphores and message queues.

A few notes:

1) These totals are calculated by calling mincore() on every file in /dev/shm and any other tmpfs filesystems.  That means that you need to have read access to those files (though it will throw a warning if you don't).  I suggest running this as root.

2) There's a discrepancy between (sysv_swp_pages + sysv_res_pages) and sysv_shm_total.  sysv_shm_total comes straight from the shmctl() call, so I don't know why this discrepancy is there.

3) System V shared memory doesn't increase the size of the cache until it's actually written to.  The POSIX behavior is more peculiar; when you open a shared memory segment with shm_open() followed by ftruncate(size) and then run pipcs, you'll see that mincore() reports the address range of the new segment as entirely in swap.  That means that if you see, say, 1G of POSIX pages in swap from pipcs output and no swap actually in use, that memory has been allocated but not written to.

4) pipcs reports whether or not System V shared memory segments are locked.  This data is not available from the kernel for POSIX shared memory segments.

Usage:

~> ./pipcs -h
./pipcs: invalid option -- 'h'
usage: pipcs [-b|-k|-m|-g] [-s]
  default: show all
  -b,-k,-m,-g show output in bytes, KB, MB, or GB
  -s show shared memory breakdown

Example output:
~> ./pipcs -sm

------ SYS V Shared Memory ------
sysv_swp_pages: 102859
sysv_swp_total: 401M
sysv_res_pages: 1210948
sysv_res_total: 4730M
sysv_lck_pages: 0
sysv_lck_total: 0M
sysv_shm_total: 7856M

------ POSIX Shared Memory ------
posix_swp_pages: 27003
posix_swp_total: 105M
posix_res_pages: 57554
posix_res_total: 224M
posix_shm_total: 330M

------ Total Shared Memory ------
total_swp_pages: 129862
total_res_pages: 1268502
shm_total:       8187M