Messages in this thread | | | Date | Wed, 09 Jul 2008 12:39:37 -0500 | From | Christoph Lameter <> | Subject | Re: [RFC 00/15] x86_64: Optimize percpu accesses |
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Jeremy Fitzhardinge wrote:
> The bulk of this series is pda_X to x86_X_percpu conversion. This seems > like pointless churn to me; there's nothing inherently wrong with the > pda_X interfaces, and doing this transformation doesn't get us any > closer to unifying 32 and 64 bit.
What is the point of the pda_X interface? It does not exist on 32 bit. The pda wastes the GS segment register on a small memory area. This patchset makes the GS segment usable to reach all of the per cpu area by placing the pda into the per cpu area. Thus the pda_X interface becomes obsolete and the 32 bit per cpu stuff becomes usable under 64 bit unifying both architectures.
> I think we should start devolving things out of the pda in the other > direction: make a series where each patch takes a member of struct > x8664_pda, converts it to a per-cpu variable (where possible, the same > one that 32-bit uses), and updates all the references accordingly. When > the pda is as empty as it can be, we can look at removing the > pda-specific interfaces.
This patchset places the whole x8664_pda structure into the per cpu area and makes the pda macros operate on the x8664_pda structure in the per cpu area. Not sure why you want to go through the churn of doing it for each object separately.
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