|| ||Mike Travis <firstname.lastname@example.org>|
|| ||Jeremy Fitzhardinge <email@example.com>|
|| ||[RFC 00/15] x86_64: Optimize percpu accesses|
|| ||Wed, 09 Jul 2008 09:51:29 -0700|
|| ||Ingo Molnar <firstname.lastname@example.org>,
Andrew Morton <email@example.com>,
"Eric W. Biederman" <firstname.lastname@example.org>,
"H. Peter Anvin" <email@example.com>,
Christoph Lameter <firstname.lastname@example.org>,
Jack Steiner <email@example.com>, 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 with following patches applied:
[PATCH 1/1] x86: Add check for node passed to node_to_cpumask V3
[PATCH 1/1] x86: Change _node_to_cpumask_ptr to return const ptr
[PATCH 1/1] sched: Reduce stack size in isolated_cpu_setup()
[PATCH 1/1] kthread: Reduce stack pressure in create_kthread and kthreadd
Signed-off-by: Christoph Lameter <email@example.com>
Signed-off-by: Mike Travis <firstname.lastname@example.org>