Hi Brice, > Well, this is interesting. numactl --hardware shows the number of > > hops, regarding to the information from that private BZ. > > I think this is wrong. numactl takes everything from sysfs as far as I > can tell. On x86, sysfs distances are ACPI SLIT latencies (memory > latencies that are normalized to 10 for latencies from one cpu to its > local memory). A couple months ago, I checked all Linux ports that show > distances in sysfs. All of them report memory latencies, except the SGI > IP27 as mentioned previously (this one indeed shows number of hops (0 > when local) and it makes a lot of sense for this architecture). >
Yes, you are absolutly right. Sorry about it. It's better to check some sources than to rely on my own memory:-) > One problem I see with the number of hops is that it doesn't make sense > on some machines. On some 8-socket AMD machines (such as > 8amd64-4n2c.tar.bz2 below) , the hypertransport route between some > sockets varies with the type of packet (response or request) and the > direction. So the number of hops ends up being asymmetric, depends on > read/write, and can be half of an integer. > Yes, this is exactly what I have seen as well. This even true for 4 socket AMD Magny Cours system. > Look at tests/linux/ in the hwloc SVN. The following tarballs contain > NUMA architectures. Some of these were gathered while running old > kernels, but I don't think it matters because Linux/sysfs reports what > the BIOS without changing much of it. > I will. The thing is that I'm pretty bu\sy right now, I need to finish a project before going on vacation. I hope to look into in September. Regards Jirka
