On 9/17/2020 1:11 PM, Bjorn Helgaas wrote: > [+cc Ingo, Peter, Juri, Vincent (scheduler maintainers)] > > s/hosekeeping/housekeeping/ (in subject) > > On Wed, Sep 09, 2020 at 11:08:16AM -0400, Nitesh Narayan Lal wrote: >> Introduce a new API num_housekeeping_cpus(), that can be used to retrieve >> the number of housekeeping CPUs by reading an atomic variable >> __num_housekeeping_cpus. This variable is set from housekeeping_setup(). >> >> This API is introduced for the purpose of drivers that were previously >> relying only on num_online_cpus() to determine the number of MSIX vectors >> to create. In an RT environment with large isolated but a fewer >> housekeeping CPUs this was leading to a situation where an attempt to >> move all of the vectors corresponding to isolated CPUs to housekeeping >> CPUs was failing due to per CPU vector limit. > > Totally kibitzing here, but AFAICT the concepts of "isolated CPU" and > "housekeeping CPU" are not currently exposed to drivers, and it's not > completely clear to me that they should be. > > We have carefully constructed notions of possible, present, online, > active CPUs, and it seems like whatever we do here should be > somehow integrated with those. > Perhaps "active" CPUs could be separated to not include the isolated CPUs?
