On Wed, Jul 18, 2018 at 11:50:33AM -0400, Rik van Riel wrote: > > On Jul 18, 2018, at 11:42 AM, Rik van Riel <r...@surriel.com> wrote: > >> On Jul 17, 2018, at 7:39 AM, Peter Zijlstra <pet...@infradead.org > >> <mailto:pet...@infradead.org>> wrote:
> >> Also, was there a reason to re-implement on_each_cpu_cond() ? (which btw > >> also wants that __cpumask_set_bit fix). > > > > I did not use on_each_cpu_cond() because I had no idea it > > existed. A quick grep suggests very few users of that function :) Yeah, only reason I know it existed was because I helped write it or something like that :-) > > I'll make sure things are done the right way. > > > OK, looking at it some more, I think open coding may be faster in > case of the TLB shootdown code, because that way we only iterate > over the CPUs in the mm_cpumask, instead of iterating over every > single online CPU in the system, and calling the helper function for > every CPU, like on_each_cpu_cond() does. > > However, the difference in overhead might be small enough that > we might not notice. Preferences? Yeah, so the difference is the case where the mask allocation fails; in that case we're under severe memory pressure and performance sucks anyway, right? In which case using on_each_cpu_cond() seems the simpler option.
