On Thu, 13 Oct 2011, KAMEZAWA Hiroyuki wrote: > sys_mem_shrink(int nid, int nr_scan_pages, int flags) > > This system call scans LRU of specified nodes and free pages on LRU. > This scan nr_scan_pages in LRU and returns the number of successfully > freed pages. > == > > Then, running this progam in SCHED_IDLE, a user can make free pages while > the system is idle. If running in the highest priority, a user can keep > free pages as he want. If a user run this under a memcg, user can free > pages in a memcg. > Satoru was specifically talking about the VM using free memory for pagecache, so doing echo echo 1 > /proc/sys/vm/drop_caches can mitigate that almost immediately. I think the key to the discussion, though, is that even the application doesn't know it's bursty memory behavior before it happens and the kernel entering direct reclaim hurts latency-sensitive applications. If there were a change to increase the space significantly between the high and min watermark when min_free_kbytes changes, that would fix the problem. The problem is two-fold: that comes at a penalty for systems or workloads that don't need to reclaim the additional memory, and it's not clear how much space should exist between those watermarks. -- 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/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>