On 05/25/2012 01:02 PM, Andrea Arcangeli wrote:
I believe (realistically speaking) nobody is going to change applications to specify which thread is using which memory (for threaded apps) with the only exception of QEMU and a few others.
This is the point of contention. I believe that for some programs these kinds of modifications might happen, but that for some other programs - managed runtimes like JVMs - it is fundamentally impossible to do proper NUMA hinting, because the programming languages that run on top of the runtimes have no concept of pointers or memory ranges, making it impossible to do those kinds of hints without fundamentally changing the programming languages in question. It would be good to get everybody's ideas out there on this topic, because this is the fundamental factor in deciding between Peter's approach to NUMA and Andrea's approach. Ingo? Andrew? Linus? Paul?
For not threaded apps that fits in a NUMA node, there's no way a blind home node can perform nearly as good as AutoNUMA:
The small tasks are easy. I suspect that either implementation can be tuned to produce good results there. It is the large programs (that do not fit in a NUMA node, either due to too much memory, or due to too many threads) that will force our hand in deciding whether to go with Peter's approach or your approach. I believe we do need to carefully think about this issue, decide on a NUMA approach based on the fundamental technical properties of each approach. After we figure out what we want to do, we can nit-pick on the codebase in question, and make sure it gets completely fixed. I am sure neither codebase is perfect right now, but both are entirely fixable. -- All rights reversed -- 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>