On Tue, Nov 20, 2012 at 10:12:28AM -0800, David Rientjes wrote: > On Mon, 19 Nov 2012, Anton Vorontsov wrote: > > > We try to make userland freeing resources when the system becomes low on > > memory. Once we're short on memory, sometimes it's better to discard > > (free) data, rather than let the kernel to drain file caches or even start > > swapping. > > > > To add another usecase: its possible to modify our version of malloc (or > any malloc) so that memory that is free()'d can be released back to the > kernel only when necessary, i.e. when keeping the extra memory around > starts to have a detremental effect on the system, memcg, or cpuset. When > there is an abundance of memory available such that allocations need not > defragment or reclaim memory to be allocated, it can improve performance > to keep a memory arena from which to allocate from immediately without > calling the kernel. > A potential third use case is a variation of the first for batch systems. If it's running low priority tasks and a high priority task starts that results in memory pressure then the job scheduler may decide to move the low priority jobs elsewhere (or cancel them entirely). A similar use case is monitoring systems running high priority workloads that should never swap. It can be easily detected if the system starts swapping but a pressure notification might act as an early warning system that something is happening on the system that might cause the primary workload to start swapping. -- Mel Gorman SUSE Labs -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>