Messages in this thread | | | Date | Wed, 28 Nov 2007 17:42:24 -0800 | From | Jeremy Fitzhardinge <> | Subject | Re: [patch 05/14] percpu: Use a Kconfig variable to configure arch specific percpu setup |
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Christoph Lameter wrote: > On Wed, 28 Nov 2007, Jeremy Fitzhardinge wrote: > > >> I don't see the problem. The way i386 does it inherently supports >> per-cpu data very early on (it uses the prototype percpu section until >> the real percpu values are set up). >> > > Ok so we could do that for x86_64 as well? There is more complicated > bootstrap since i386 does not support NUMA aware placement of per cpu > areas. >
Don't think it matters either way. Before percpu is allocated, NUMA issues don't matter. Once they are - by whatever mechanism - you can set the segment bases up appropriately. The fact that you chose to put percpu data at address X doesn't affect the percpu mechanism one way or the other.
> percpu references are quite frequent already (vm statistics) and will be > more frequent after we have converted the per cpu arrays to per cpu > allocations. >
Well, I think the point is moot, because x86 will always use 32-bit offsets. Each reference will only be 1 byte bigger than a normal variable reference.
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