On Friday, October 29, 2010 10:59:25 pm Brice Goglin wrote: > Le 29/10/2010 21:57, Jirka Hladky a écrit : > > Hi Samuel, > > > > I have attached the output of > > tests/linux/gather-topology.sh `uname --kernel-release`_`uname -- > > nodename`_gather-topology > > > > I'm sorry for the long delay - systems has been used by somebody else, I > > had to wait for it to be free. > > > > System is running kernel 2.6.18-227.el5 (RHEL 5.6). ia64 is not supported > > on RHEL 6.0 so I cannot really test it on the new kernel. > > > > It would be really interesting if you can recognize if it's a kernel bug > > or hwloc problem. > > /sys/devices/system/cpu/cpu*/cache/index4/shared_cpu_map contains an > empty map. This index4 is a L3 cache. But this map means that this cache > is near none of the cores... The instruction L2 has the same problem > (index3 instead of 4). This is a kernel bug. > > But, we already have a dedicated work-around in hwloc > (src/topology-linux.c): > if (hwloc_bitmap_weight(cacheset) < 1) > /* mask is wrong (happens on ia64), assumes it's not shared */ > hwloc_bitmap_only(cacheset, i); > > This work-around worked fine on old itaniums since they had one L3, one > L2 and one L1 per core. Your machine has hyperthreading, so our > work-around creates one L3 per thread, while L1 and L2 (properly > reported by the kernel) are core-specific. Maybe hwloc should just > ignore caches with invalid shared_cpu_map. > > Brice > > _______________________________________________ > hwloc-devel mailing list > hwloc-de...@open-mpi.org > http://www.open-mpi.org/mailman/listinfo.cgi/hwloc-devel
Hi Brice, thanks for looking into it! I'm going to open a BZ for it and put you on the Cc. BTW, is there some documentation on /sys/devices/system/cpu/* tree? Thanks! Jirka
