Messages in this thread | | | Date | Thu, 9 Oct 2008 10:06:01 +0200 | From | Andi Kleen <> | Subject | Re: [PATCH] rudimentary tracing for Classic RCU |
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On Thu, Oct 09, 2008 at 04:14:26PM +0900, KOSAKI Motohiro wrote: > Hi Lai-san, > > > >> In this case, why not define it as: > > >> static char buf[20*NR_CPUS + 100]; > > > > > > Actually you should near never use NR_CPUS now but always num_possible_cpus() > > > (or even num_online_cpus()) Using NR_CPUS can lead to extreme waste > > > of memory on kernels which are compiled for 4096 CPUs for example. > > > > > > And with num_possible_cpus() kmalloc is needed. > > > > I thought the default value of NR_CPUS is 32. > > it's pointless. > Almost distribution use _very_ large NR_CPUS (likes 4096).
Right now it's more like 8-128, but at least there is some effort to make a 4096 CPU distribution possible and Mike Travis has been tirelessly working on eradicating all the rogue NR_CPUs all over the tree. So it's better to not add more.
> So, We should concern large NR_CPUS.
Agreed.
-Andi
-- ak@linux.intel.com
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