Messages in this thread | | | Subject | Re: [RFC 3/4] ARM: topology: Update cpu_power according to DT information | From | Peter Zijlstra <> | Date | Wed, 13 Jun 2012 18:06:48 +0200 |
| |
On Wed, 2012-06-13 at 16:54 +0200, Vincent Guittot wrote: > On 13 June 2012 15:07, Peter Zijlstra <peterz@infradead.org> wrote: > > On Tue, 2012-06-12 at 14:02 +0200, Vincent Guittot wrote: > >> +struct cpu_capacity cpu_capacity[NR_CPUS]; > > > > I know ARM isn't likely to suffer from the 4k cpu issue, but is there a > > reason to use a NR_CPUS array over a per-cpu variable? > > At this stage, we don't know which logical CPU will match which hwid. > During the boot of each CPU, we parse the table to found an efficiency > value for the booting CPU. The whole table is used by one CPU at a > time.
Its not so much the usage as the dynamic sizing that I was after. NR_CPUS will always be the max size, whereas per-cpu data will only use the amount of storage required to back the number of cpus present.
For this reason we've spend a great deal of effort to remove NR_CPUS sized arrays all over the core (and x86/ia64 arch) code, since distros now build with NR_CPUS=4096 but hardly anybody has that many cpus, so arrays sized that way waste tons of resources.
| |