On Wed, Mar 13, 2024 at 11:48:19AM +0100, Anthony Harivel wrote: > Hi Daniel, > > Daniel P. Berrangé, Mar 12, 2024 at 16:49: > > > The point still stands though. NUMA node ID numbers are not > > guaranteed to be the same as socket ID numbers. Very often > > then will be the same (which makes it annoying to test as it > > is easy to not realize the difference), but we can't rely on > > that. > > > > > I'm using functions of libnuma to populate the maxpkgs of the host. > > > I tested this on different Intel CPU with multiple packages and this > > > has always returned the good number of packages. A false positive ? > > > > maxpkgs comes from vmsr_get_max_physical_package() which you're > > reading from sysfs, rather than libnuma. > > > > > So here I'm checking if the thread has run on the package number 'i'. > > > I populate 'numa_node_id' with numa_node_of_cpu(). > > > > > > I did not wanted to reinvent the wheel and the only lib that was talking > > > about "node" was libnuma. > > > > I'm not actually convinced we need to use libnuma at all. IIUC, you're > > just trying to track all CPUs within the same physical socket (package). > > I don't think we need to care about NUMA nodes to do that tracking. > > > > Alright, having a deeper look I'm actually using NUMA for 2 info: > > - How many cpu per Package: this helps me calculate the ratio. > > - To whom package the cpu belongs: to calculate the ratio with the right > package energy counter. > > Without libnuma, I'm bit confused on how to handle this. > > Should I parse /sys/bus/node/devices/node* to know how many packages ? > Should I parse /sys/bus/node/devices/node0/cpu0/topology/core_cpus_list > to handle which cpu belongs to which package ?
You don't need to access it via the /node/ hierarchy The canonical path for CPUs would be /sys/devices/system/cpu/cpuNNN/topology The core_cpus_list file is giving you hyper-thread siblings within a core, which I don't think is what you want. If you're after discrete physical packages, then 'package_cpus_list' gives you all CPUs within a physical socket (package) I believe. > Would that be too cumbusome for the user to enter the detail about how > many packages and how many cpu per pakages ? > > i.e: > -kvm,rapl=true,maxpkgs=2,cpupkgs=8,rapl-helper-socket=/path/sock.sock That won't cope with asymmetrical CPU configurations, so I think it is preferrable to read the info from sysfs. With regards, Daniel -- |: https://berrange.com -o- https://www.flickr.com/photos/dberrange :| |: https://libvirt.org -o- https://fstop138.berrange.com :| |: https://entangle-photo.org -o- https://www.instagram.com/dberrange :|
