lkml.org 
[lkml]   [2008]   [Jul]   [9]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [RFC 00/15] x86_64: Optimize percpu accesses
    Christoph Lameter wrote:
    > 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.

    I think Jeremy's point is that by removing the pda struct entirely, the
    references to the fields can be the same for both x86_32 and x86_64.

    Thanks,
    Mike


    \
     
     \ /
      Last update: 2008-07-09 20:05    [W:0.022 / U:32.784 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site