Andi Kleen wrote: >>> Topology is dependent on the number of CPUs. >> Not all of it. > > What is not?
Memory banks can exist without a CPU present. The places where you can plug in memory don't change and so the memory hierarchy can be described. > Hmm, e.g. in OpenMP you would have another thread that just reads > /proc/cpuinfo > in a loop and starts new threads on new CPUs? > > That sounds ...... "expensive" That's the cost of doing business. There is an inexpensive solution: finally make the vdso concept a bit more flexible. You could add a vdso call to get the processor count. The vdso code itself can use a data page mapped in from the kernel. This page (read-only at userlevel) would contain global information such as processor count and topology. But we're getting IMO off topic here. That's a separate and far more complicated issue. Here we now have the concrete issue that determining the CPU count is terribly expensive and there is a simple proposal to make it faster by keeping /sys/devices/system/cpu/ free from anything but cpu* directories. -- ➧ Ulrich Drepper ➧ Red Hat, Inc. ➧ 444 Castro St ➧ Mountain View, CA ❖
signature.asc
Description: OpenPGP digital signature
