On Fri, 4 Sep 2009, [email protected] wrote: > you can change this default to disable overcommit. in which case if you do > not have the address space available to fully support all possible COW > splits. if you don't have enough swap allocated to support the possible
Hi David. Catching up on mail from last week :) The overcommitt accounting would be very inefficient if it worked as you describe above (assuming I'm not misunderstanding what you've written). The overcommit accounting rules can be found here: http://www.mjmwired.net/kernel/Documentation/vm/overcommit-accounting In particular non-private shared memory pages (that could be subject to COW) count only once for purposes of overcommit. Unlimited overcommit comes in to play for applications that ask for large memory allocations but do not use them. Certain DB apps are quite notable here. They ask for large memory allocations which they will probably never use. Without unlimited overcommit the application startup will fail even though it would run fine were it allowed to start. Cheers, Rob -- I tried to change the world but they had a no-return policy http://www.practicalsysadmin.com _______________________________________________ Tech mailing list [email protected] http://lopsa.org/cgi-bin/mailman/listinfo/tech This list provided by the League of Professional System Administrators http://lopsa.org/
