Hi Dan, On 04/12/2013 08:29 AM, Dan Magenheimer wrote:
MM developers and all -- It's a bit late to add a topic, but with such a great group of brains together, it seems worthwhile to spend at least some time speculating on "farther-out" problems. So I propose for the MM track: Beyond NUMA NUMA now impacts even the smallest servers and soon, perhaps even embedded systems, but the performance effects are limited when the number of nodes is small (e.g. two). As the number of nodes grows, along with the number of memory controllers, NUMA can have a big performance impact and the MM community has invested a huge amount of energy into reducing this problem. But as the number of memory controllers grows, the cost of the system grows faster. This is classic "scale-up" and certain workloads will always benefit from having as many CPUs/cores and nodes as can be packed into a single system. System vendors are happy to oblige because the profit margin on scale-out systems can be proportionally much much larger than on smaller commodity systems. So the NUMA work will always be necessary and important. But as scale-out grows to previously unimaginable levels, an increasing fraction of workloads are unable to adequately benefit to compensate for the non-linear increase in system cost. And so more users, especially cost-sensitive users, are turning instead to scale-out to optimize cost vs benefit for their massive data centers. Recent examples include HP's Moonshot and Facebook's "Group Hug". And even major data center topology changes are being proposed which use super-high-speed links to separate CPUs from RAM [1]. While filesystems and storage have long ago adapted to handle large numbers of servers effectively, the MM subsystem is still isolated, managing its own private set of RAM, independent of and completely partitioned from the RAM of other servers. Perhaps we, the Linux MM developers, should start considering how MM can evolve in this new world. In some ways, scale-out is like NUMA, but a step beyond. In other ways, scale-out is very different. The ramster project [2] in the staging tree is a step in the direction of "clusterizing" RAM, but may or may not be the right step.
If I configure UMA machine to fake numa, is there benefit or impact performance?
Discuss. [1] http://allthingsd.com/20130410/intel-wants-to-redesign-your-server-rack/ [2] http://lwn.net/Articles/481681/ (see y'all next week!) -- 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=ilto:"dont@xxxxxxxxx"> email@xxxxxxxxx </a>
-- 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>