|| ||Mike Travis <firstname.lastname@example.org>|
|| ||Ingo Molnar <email@example.com>, Jeremy Fitzhardinge <firstname.lastname@example.org>,
"Eric W. Biederman" <email@example.com>|
|| ||[RFC 0/5] percpu: Optimize percpu accesses|
|| ||Tue, 01 Jul 2008 05:16:34 -0700|
|| ||Christoph Lameter <firstname.lastname@example.org>,
"H. Peter Anvin" <email@example.com>,
Andrew Morton <firstname.lastname@example.org>,
This patchset provides the following:
* Cleanup: Fix early references to cpumask_of_cpu(0)
Provides an early cpumask_of_cpu(0) usable before the cpumask_of_cpu_map
is allocated and initialized.
* 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.
(Note: split into two patches, one to rebase percpu variables at 0,
and the second to actually use %gs as the base for percpu variables.)
* 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
%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/master
Signed-off-by: Christoph Lameter <email@example.com>
Signed-off-by: Mike Travis <firstname.lastname@example.org>