Messages in this thread | | | Date | Mon, 6 Nov 2006 13:20:29 -0800 | From | Andrew Morton <> | Subject | Re: Avoid allocating during interleave from almost full nodes |
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On Mon, 6 Nov 2006 12:58:52 -0800 (PST) Christoph Lameter <clameter@sgi.com> wrote:
> > OK, but if two nodes have a lot of free pages and the rest don't then > > interleave will consume those free pages without performing any reclaim > > from all the other nodes. Hence hostpots or imbalances. > > > > Whatever they are. Why does it matter? > > Hotspots create lots of requests going to the same numa node. The nodes > have a limited capability to service cacheline requests and the bandwidth > on the interlink is also limited. If too many processors request > information from the same remote node then performance will drop.
OK.
> There are different kind of data in a NUMA system: > > Data that is node local is only accessed by the local processor. For node > local data we have no such concerns since the interlink is not used. Quite > a lot of kernel data per node or per cpu and thus is not a problem. > > For shared data that is known to be performance critical--and where we > know that the data is accessed from multiple nodes--there we need to > balance the data between multiple nodes to avoid overloads and > to keep the system running at optimal speed. That is where interleave > becomes important.
But doesn't this patch introduce considerable risks of the above problems occurring? In the two-nodes-have-lots-of-free-memory scenario? - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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