[PATCH 00/20] powerpc/8xx: Use large pages for RAM and IMMR and other improvments.

From: Christophe Leroy
Date: Wed Aug 12 2015 - 09:47:28 EST

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

Christophe Leroy (20):
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
powerpc/8xx: Fix vaddr for IMMR early remap
powerpc32: iounmap() cannot vunmap() area mapped by TLBCAMs either
powerpc32: refactor x_mapped_by_bats() and x_mapped_by_tlbcam()
powerpc/8xx: Map IMMR area with 512k page at a fixed address
powerpc/8xx: show IMMR area in startup memory layout
powerpc/8xx: map 16M RAM at startup
powerpc/8xx: move 8xx SPRN defines into reg_8xx.h and add some missing
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
powerpc32: Remove clear_pages()
powerpc32: Remove useless/wrong MMU:setio progress message
powerpc/8xx: also use r3 in the ITLB miss in all situations
powerpc32: remove ioremap_base

Documentation/kernel-parameters.txt | 2 +-
arch/powerpc/Kconfig.debug | 2 -
arch/powerpc/include/asm/mmu-8xx.h | 26 ++--
arch/powerpc/include/asm/page_32.h | 3 +-
arch/powerpc/include/asm/pgtable-ppc32.h | 5 +
arch/powerpc/include/asm/reg.h | 2 +
arch/powerpc/include/asm/reg_8xx.h | 106 ++++++++++++++++
arch/powerpc/include/asm/time.h | 6 +-
arch/powerpc/kernel/head_8xx.S | 151 +++++++++-------------
arch/powerpc/kernel/misc_32.S | 17 +--
arch/powerpc/kernel/ppc_ksyms_32.c | 1 -
arch/powerpc/mm/8xx_mmu.c | 190 ++++++++++++++++++++++++++++
arch/powerpc/mm/Makefile | 1 +
arch/powerpc/mm/init_32.c | 23 ----
arch/powerpc/mm/mem.c | 4 +
arch/powerpc/mm/mmu_decl.h | 16 +--
arch/powerpc/mm/pgtable_32.c | 54 +++++++-
arch/powerpc/platforms/embedded6xx/mpc10x.h | 8 --
18 files changed, 444 insertions(+), 173 deletions(-)
create mode 100644 arch/powerpc/mm/8xx_mmu.c


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