Messages in this thread | | | Subject | Re: [PATCH v6 2/3] percpu: add PERCPU_ATOM_SIZE for a generic percpu area setup | From | Jungseok Lee <> | Date | Tue, 3 Nov 2015 23:11:16 +0900 |
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On Nov 3, 2015, at 1:10 AM, Christoph Lameter wrote:
Dear Christoph,
> On Sun, 1 Nov 2015, Jungseok Lee wrote: > >> There is no room to adjust 'atom_size' now when a generic percpu area >> is used. It would be redundant to write down an architecture-specific >> setup_per_cpu_areas() in order to only change the 'atom_size'. Thus, >> this patch adds a new definition, PERCPU_ATOM_SIZE, which is PAGE_SIZE >> by default. The value could be updated if needed by architecture. > > What is atom_size? Why would you want a difference allocation size here? > The percpu area is virtually mapped regardless. So you will have > contiguous addresses even without atom_size.
I think Catalin have already written down a perfect explanation. I'd like memory with an alignment greater than PAGE_SIZE. But, __per_cpu_offset[] is PAGE_SIZE aligned under a generic setup_per_cpu_areas(). That is, secondary cores cannot get that kind of space.
Thanks for taking a look at this doubtable change!
Best Regards Jungseok Lee
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