On Fri, 31 May 2013 18:44:03 +0200 Damien Millescamps <damien.millescamps at 6wind.com> wrote:
> On 05/31/2013 05:45 PM, Stephen Hemminger wrote: > > This was confirmed by several kernel developers including Andi Kleen from > > Intel. The value in /proc/cpuinfo comes from the APCI tables and is the > > value > > reported by the BIOS. There are machines that report socket 1 and 2. > > Haven't played with older kernels, but the topology information in sysfs > > has existed since 2.6.16. > Hi Stephen, > > You didn't really address my point, because the Linux documentation says > something doesn't mean it works in the real world. > > If you take the example of the hugepages, they have been in the Linux > kernel since 2.6.28, but the last fix was pushed in 2.6.37 and before > 2.6.33 it is just impossible to do something with hugepages. > If you take a look at section 2.3.2 of the DPDK getting started: > http://www.intel.com/content/dam/www/public/us/en/documents/guides/intel-dpdk-getting-started-guide.pdf, > you will find that this issue is at least partially addressed. > > So the point is that the topology information being theoretically > correct on all kernel Linux supported by the DPDK, but the information > being practically wrong on versions prior to kernel 3.3 means that the > "fix" is breaking the support for a quite huge range of kernel versions... > So maybe there might be a better way to get this node information on all > kernel still currently supported by the DPDK. > > Cheers, I will just state what we saw. /proc/cpuinfo was wrong on several Dell machines but sysfs is correct. And since are working on a product, not generic DPDK, there is no motivation to work on older kernels. I can dig out the email back and forth with the kernel developers to show that /proc/cpuinfo is not intended to report anything useful for NUMA related API if you want.
