Messages in this thread | | | Date | Wed, 12 Jun 2002 10:36:11 +0200 | From | Helge Hafting <> | Subject | Re: [PATCH] 2.5.21 Nonlinear CPU support |
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Andrew Morton wrote: > > Rusty Russell wrote: > > > > ... > > Let's not perpetuate the myth that everything in the kernel needs to > > be tuned to the last cycle at all costs, hm? > > I was more concerned about the RAM use, actually. > > This patch is an additional reason for CONFIG_NR_CPUS, but I've rather > gone cold on that idea because the "proper fix" is to make all those > huge per-cpu arrays dynamically allocated. So you can run a 64p kernel > on 2p without losing hundreds of k of memory and kernel address space. > > But it looks like all those dynamically-allocated structures would > have to be allocated out to NR_CPUS anyway, to support hotplug, yes? > > In which case, CONFIG_NR_CPUS is the only way to get the memory > back...
Re-allocation of tables when adding CPUs is another option. That means the data moves - so others have to store array indices instead of direct pointers to stuff they use. Dynamic allocation not merely at boottime, but everytime.
Adding a CPU becomes more expensive, but that won't happen hundreds of times a second anyway.
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