[Crash-utility] Crash dump of RHEL5, what does "SHARED" memory represent in kmem -i output?

[anderson at prospeed.net]

> From: James Washer <washer at trlp.com>
> To: Crash-utility at redhat.com
> Subject: [Crash-utility] Crash dump of RHEL5,	what does "SHARED"
> 	memory represent in kmem -i output?
> Message-ID: <E06C76EC-884A-4C02-9566-D647E0B575CA at trlp.com>
> Content-Type: text/plain; charset=us-ascii
>
> In the data below, what memory usage is reported as SHARED? Does this
> imply SysV shared memory, or pages shared between processes, or something
> else all together?
>
>
> kmem-i
>
>               PAGES        TOTAL      PERCENTAGE
>  TOTAL MEM  9228936      35.2 GB         ----
>       FREE    20260      79.1 MB    0% of TOTAL MEM
>       USED  9208676      35.1 GB   99% of TOTAL MEM
>     SHARED  9051322      34.5 GB   98% of TOTAL MEM
>    BUFFERS      151       604 KB    0% of TOTAL MEM
>     CACHED     2455       9.6 MB    0% of TOTAL MEM
>       SLAB    27419     107.1 MB    0% of TOTAL MEM
>
> TOTAL HIGH        0            0    0% of TOTAL MEM
>  FREE HIGH        0            0    0% of TOTAL HIGH
>  TOTAL LOW  9228936      35.2 GB  100% of TOTAL MEM
>   FREE LOW    20260      79.1 MB    0% of TOTAL LOW
>
> TOTAL SWAP  4194302        16 GB         ----
>  SWAP USED  2294571       8.8 GB   54% of TOTAL SWAP
>  SWAP FREE  1899731       7.2 GB   45% of TOTAL SWAP
>
>
>
>  - jim

Hi Jim,

Purportedly it displays -- as the comment states:

 /*
  *  Get shared pages from dump_mem_map().  Note that this is done
  *  differently than the kernel -- it just tallies the non-reserved
  *  pages that have a count of greater than 1.
  */

It has a check in there for the different usage of page->count,
where in certain kernel versions, -1 means 0.

Dave Anderson  (on vacation)