Comments on: Shared Memory In Linux

By: Neil

Neil — Mon, 15 Dec 2008 11:18:28 +0000

Hi!
Dave , I am trying to implement linked list in shared memory , however I am facing problem. If I have a prev and next pointer , what shall it contain the offset from start of the shared memory address ?? this is okay only if my nodes are not same in size , otherwise having next and prev pointers are redundant as incrementing and decrementing by node size can get me the previous and next node. Any help in this regard will be useful. TX

By: dave

dave — Sat, 10 May 2008 18:59:36 +0000

Thanks for the info, I think this solves a problem for me. I create linked lists [that is chained structure] in a shared memory seg. First program loads the data [lots of it about 10 lists including processes to start into shm. second process [an exec] reads the data in the shm, sets up coms to about 100 remote nodes, fires up processes local and remote , and supervises the “system”. Only under linux the second process cannot see the linked list. The start of a list is a fixed offset from the start of shm but the back and next pointers of the next “link” point to locations with junk. No data, no valid next. I will try this shm file to see if it will get me out of a problem. I ran your test code and it looks good. So again thanks for the info. best regards, (dja.)

By: tom

tom — Mon, 18 Feb 2008 21:53:46 +0000

Do you have a source for the “heavy performance penalty”?