We need to create a large (~100M) contiguous physical memory region which will only be needed occasionally. As this region will use up 10-20% of all of the available memory, we do not want to pre-reserve it at boot time. Instead, we want to create this memory region "on the fly" when asked to by userspace, and do it as quickly as possible, and return it to system use when not needed. AFAIK, this sort of operation is currently done using memory compaction (as CMA does for instance). Alternatively, this memory region (if it is in a fixed place) could be created using "logical memory hotremove" and returned to the system using "logical memory hotplug". In either case, the contiguous physical memory would be created via migrating pages from the "movable zone". The problem with this approach is that the copying of up to 25000 pages may take considerable time (as well as finding destinations for all of the pages if free memory is scarce -- this may even fail, causing the memory region not to be created). It was suggested to me that a new zone type which would be similar to the "movable zone" but is only allowed to contain pages that can be discarded (such as text) could solve this problem, so that there is no copying or finding destination pages needed (thus considerably reducing latency). The downside I see is that there may not be anywhere near 25000 such discardable pages, so most of this zone would go unused, and the memory would be "wasted" as in the case where it is pre-reserved. Also, this is not currently supported, so new code would have to be designed and implemented. I would appreciate people's comments about: 1. Does this type of zone make any sense? It would have to co-exist with the current movable zone type. 2. How hard would it be to implement this? The new zone type would need to be supported and "discardable" pages steered into this zone. 3. Are there better ways of allocating a large memory region with minimal latency that I haven't mentioned here? Thanks. Larry Bassel -- Sent by an employee of the Qualcomm Innovation Center, Inc. The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum. -- 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>