Messages in this thread | | | Date | Fri, 13 Dec 2019 09:10:33 +0100 | From | Peter Zijlstra <> | Subject | Re: [PATCH] sched/fair: Optimize select_idle_cpu |
| |
On Fri, Dec 13, 2019 at 09:51:30AM +0800, chengjian (D) wrote: > Hi, Peter > > I saw the same work in select_idle_core, and I was wondering why the > per_cpu variable was > > needed for this yesterday. Now I think I probably understand : cpumask may > be too large, > > putting it on the stack may cause overflow. Is this correct ?
Yes, for instance when NR_CPUS=4096, struct cpumask ends up being 512 bytes, and that is _far_ too large for an on-stack variable, remember we have relatively small fixed size stacks.
| |