> On Mar 1, 2021, at 9:10 AM, Peter Zijlstra <pet...@infradead.org> wrote: > > On Sat, Feb 20, 2021 at 03:17:04PM -0800, Nadav Amit wrote: >> + /* >> + * Choose the most efficient way to send an IPI. Note that the >> + * number of CPUs might be zero due to concurrent changes to the >> + * provided mask. >> + */ >> + if (nr_cpus == 1) >> + arch_send_call_function_single_ipi(last_cpu); >> + else if (likely(nr_cpus > 1)) >> + arch_send_call_function_ipi_mask(cfd->cpumask_ipi); > > I just ran into conflicts with another patch set, and noticed that the > above should probably be: > > if (nr_cpus == 1) > send_call_function_single_ipi(last_cpu); > else if (likely(nr_cpus > 1)) > arch_send_call_function_ipi_mask(cfd->cpumask_ipi); > > Which will avoid the IPI when @last_cpu is idle.
Good point. Makes one wonder whether all these inter-core communication (through cpu_tlbstate.is_lazy, csd->node.llist and ti->flags) are really necessary or can be combined. Well, that’s for later I presume.
