[PATCH 0/6] powerpc: SMT priority (PPR) save and restore

Haren Myneni haren at linux.vnet.ibm.com
Wed Oct 31 17:49:31 EST 2012

[PATCH 0/6] powerpc: SMT priority (PPR) save and restore

On P7 systems, users can define SMT priority levels 2,3 and 4 for
processes so that some can run higher priority than the other ones.
In the current kernel, the default priority is set to 4 which prohibits
processes for using higher priority. Also the kernel boosts the priority to
4 during exceptions without saving the user defined priorities when
the task enters the kernel. So we will be loosing the process PPR value
and can not be restored it back when the task exits the kernel.

This patchset implements saving and restore the user defined PPR value
for all tasks.

With null_syscall testcase (http://ozlabs.org/~anton/junkcode/null_syscall.c),
this feature takes around extra 10 CPU cycles on average for 25 samples. 

Haren Myneni (6):
  powerpc: Move branch instruction from ACCOUNT_CPU_USER_ENTRY to caller
  powerpc: Define CPU_FTR_HAS_PPR
  powerpc: Increase exceptions arrays in paca struct to save PPR
  powerpc: Define ppr in thread_struct
  powerpc: Macros for saving/restore PPR
  powerpc: Implement PPR save/restore

 arch/powerpc/include/asm/cputable.h      |    6 ++-
 arch/powerpc/include/asm/exception-64s.h |   45 ++++++++++++++++++++++++++----
 arch/powerpc/include/asm/paca.h          |    6 ++--
 arch/powerpc/include/asm/ppc_asm.h       |   27 ++++++++++++++++-
 arch/powerpc/include/asm/processor.h     |    6 ++++
 arch/powerpc/include/asm/reg.h           |    1 +
 arch/powerpc/kernel/asm-offsets.c        |    1 +
 arch/powerpc/kernel/entry_64.S           |    6 +++-
 arch/powerpc/kernel/exceptions-64e.S     |    3 +-
 arch/powerpc/kernel/exceptions-64s.S     |   15 +++++----
 arch/powerpc/kernel/process.c            |    2 +
 11 files changed, 96 insertions(+), 22 deletions(-)

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