Messages in this thread |  | | | Date | Tue, 03 Jun 2008 17:30:18 -0700 | | From | Mike Travis <> | | Subject | [PATCH 0/4] percpu: Optimize percpu accesses |
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This patchset provides the following:
* Generic: Percpu infrastructure to rebase the per cpu area to zero
This provides for the capability of accessing the percpu variables using a local register instead of having to go through a table on node 0 to find the cpu-specific offsets. It also would allow atomic operations on percpu variables to reduce required locking. Uses a new config var HAVE_ZERO_BASED_PER_CPU to indicate to the generic code that the arch has this new basing.
* x86_64: Fold pda into per cpu area
Declare the pda as a per cpu variable. This will move the pda area to an address accessible by the x86_64 per cpu macros. Subtraction of __per_cpu_start will make the offset based from the beginning of the per cpu area. Since %gs is pointing to the pda, it will then also point to the per cpu variables and can be accessed thusly:
%gs:[&per_cpu_xxxx - __per_cpu_start] * x86_64: Rebase per cpu variables to zero
Take advantage of the zero-based per cpu area provided above. Then we can directly use the x86_32 percpu operations. x86_32 offsets %fs by __per_cpu_start. x86_64 has %gs pointing directly to the pda and the per cpu area thereby allowing access to the pda with the x86_64 pda operations and access to the per cpu variables using x86_32 percpu operations.
Based on linux-2.6.tip
Signed-off-by: Christoph Lameter <clameter@sgi.com> Signed-off-by: Mike Travis <travis@sgi.com> --- --
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