Messages in this thread |  | | | Date | Thu, 9 Feb 2006 03:32:55 -0500 | | From | Chuck Ebbert <> | | Subject | Re: [PATCH] percpu data: only iterate over possible CPUs |
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In-Reply-To: <20060208204502.12513ae5.akpm@osdl.org>
On Wed, 8 Feb 2006 at 20:45:02 -0800, Andrew Morton wrote:
> > Its even documented in line 332 of include/linux/cpumask.h > > > > * #ifdef CONFIG_HOTPLUG_CPU > > * cpu_possible_map - all NR_CPUS bits set > > That seems a quite bad idea. If we know which CPUs are possible we should > populate cpu_possible_map correctly, whether or not CONFIG_HOTPLUG_CPU is > set.
I don't think that's, um, "possible." Even if you could discover how many empty sockets there were in a system, someone might be able to hotplug a board with more of them on it. And there's no way to tell how many CPUs to reserve for each socket anyway, e.g. AMD has already announced quad-core processors.
But what really surprised me is that for_each_cpu() actually walks cpu_possible_map and not cpu_present_map as I had assumed. This violates the Principle Of Least Surprise. Maybe renaming for_each_cpu to for_each_possible_cpu might be a good idea?
-- Chuck "Equations are the Devil's sentences." --Stephen Colbert
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