[PATCH v8 00/23] powerpc/8xx: Use large pages for RAM and IMMR and other improvments

Christophe Leroy christophe.leroy at c-s.fr
Wed Feb 10 03:07:45 AEDT 2016

The main purpose of this patchset is to dramatically reduce the time
spent in DTLB miss handler. This is achieved by:
1/ Mapping RAM with 8M pages
2/ Mapping IMMR with a fixed 512K page

On a live running system (VoIP gateway for Air Trafic Control), over
a 10 minutes period (with 277s idle), we get 87 millions DTLB misses
and approximatly 35 secondes are spent in DTLB handler.
This represents 5.8% of the overall time and even 10.8% of the
non-idle time.
Among those 87 millions DTLB misses, 15% are on user addresses and
85% are on kernel addresses. And within the kernel addresses, 93%
are on addresses from the linear address space and only 7% are on
addresses from the virtual address space.

Once the full patchset applied, the number of DTLB misses during the
period is reduced to 11.8 millions for a duration of 5.8s, which
represents 2% of the non-idle time.

This patch also includes other miscellaneous improvements:
1/ Handling of CPU6 ERRATA directly in mtspr() C macro to reduce code
specific to PPC8xx
2/ Rewrite of a few non critical ASM functions in C
3/ Removal of some unused items

See related patches for details

Main changes in v3:
* Using fixmap instead of fix address for mapping IMMR

Change in v4:
* Fix of a wrong #if notified by kbuild robot in 07/23

Change in v5:
* Removed use of pmd_val() as L-value
* Adapted to match the new include files layout in Linux 4.5

Change in v6:
* Removed remaining use of pmd_val() as L-value (reported by kbuild test robot)

Change in v7:
* No change (commit error)

Change in v8:
* Don't include x_block_mapped() from compilation in
arch/powerpc/mm/fsl_booke_mmu.c when CONFIG_FSL_BOOKE is not set
(reported by kbuild test robot)

Christophe Leroy (23):
  powerpc/8xx: Save r3 all the time in DTLB miss handler
  powerpc/8xx: Map linear kernel RAM with 8M pages
  powerpc: Update documentation for noltlbs kernel parameter
  powerpc/8xx: move setup_initial_memory_limit() into 8xx_mmu.c
  powerpc32: Fix pte_offset_kernel() to return NULL for bad pages
  powerpc32: refactor x_mapped_by_bats() and x_mapped_by_tlbcam()
  powerpc/8xx: Fix vaddr for IMMR early remap
  powerpc/8xx: Map IMMR area with 512k page at a fixed address
  powerpc/8xx: CONFIG_PIN_TLB unneeded for CONFIG_PPC_EARLY_DEBUG_CPM
  powerpc/8xx: map more RAM at startup when needed
  powerpc32: Remove useless/wrong MMU:setio progress message
  powerpc32: remove ioremap_base
  powerpc/8xx: Add missing SPRN defines into reg_8xx.h
  powerpc/8xx: Handle CPU6 ERRATA directly in mtspr() macro
  powerpc/8xx: remove special handling of CPU6 errata in set_dec()
  powerpc/8xx: rewrite set_context() in C
  powerpc/8xx: rewrite flush_instruction_cache() in C
  powerpc: add inline functions for cache related instructions
  powerpc32: Remove clear_pages() and define clear_page() inline
  powerpc32: move xxxxx_dcache_range() functions inline
  powerpc: Simplify test in __dma_sync()
  powerpc32: small optimisation in flush_icache_range()
  powerpc32: Remove one insn in mulhdu

 Documentation/kernel-parameters.txt          |   2 +-
 arch/powerpc/Kconfig.debug                   |   1 -
 arch/powerpc/include/asm/cache.h             |  19 +++
 arch/powerpc/include/asm/cacheflush.h        |  52 ++++++-
 arch/powerpc/include/asm/fixmap.h            |  14 ++
 arch/powerpc/include/asm/mmu-8xx.h           |   4 +-
 arch/powerpc/include/asm/nohash/32/pgtable.h |   5 +-
 arch/powerpc/include/asm/page_32.h           |  17 ++-
 arch/powerpc/include/asm/reg.h               |   2 +
 arch/powerpc/include/asm/reg_8xx.h           |  93 ++++++++++++
 arch/powerpc/include/asm/time.h              |   6 +-
 arch/powerpc/kernel/asm-offsets.c            |   8 ++
 arch/powerpc/kernel/head_8xx.S               | 207 +++++++++++++++++----------
 arch/powerpc/kernel/misc_32.S                | 107 ++------------
 arch/powerpc/kernel/ppc_ksyms.c              |   2 +
 arch/powerpc/kernel/ppc_ksyms_32.c           |   1 -
 arch/powerpc/mm/8xx_mmu.c                    | 190 ++++++++++++++++++++++++
 arch/powerpc/mm/Makefile                     |   1 +
 arch/powerpc/mm/dma-noncoherent.c            |   2 +-
 arch/powerpc/mm/fsl_booke_mmu.c              |   6 +-
 arch/powerpc/mm/init_32.c                    |  23 ---
 arch/powerpc/mm/mmu_decl.h                   |  34 +++--
 arch/powerpc/mm/pgtable_32.c                 |  47 +-----
 arch/powerpc/mm/ppc_mmu_32.c                 |   4 +-
 arch/powerpc/platforms/embedded6xx/mpc10x.h  |  10 --
 arch/powerpc/sysdev/cpm_common.c             |  15 +-
 26 files changed, 585 insertions(+), 287 deletions(-)
 create mode 100644 arch/powerpc/mm/8xx_mmu.c


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