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

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Date:	Wed, 12 Aug 2015 15:40:52 +0200 (CEST)
From:	Christophe Leroy <christophe.leroy@....fr>
To:	Benjamin Herrenschmidt <benh@...nel.crashing.org>,
	Paul Mackerras <paulus@...ba.org>,
	Michael Ellerman <mpe@...erman.id.au>, scottwood@...escale.com,
	Jonathan Corbet <corbet@....net>
Cc:	linux-kernel@...r.kernel.org, linuxppc-dev@...ts.ozlabs.org,
	Joakim Tjernlund <joakim.tjernlund@...nsmode.se>,
	linux-doc@...r.kernel.org
Subject: [PATCH 00/20] powerpc/8xx: Use large pages for RAM and IMMR and other improvments.

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()
    together
  powerpc/8xx: Map IMMR area with 512k page at a fixed address
  powerpc/8xx: show IMMR area in startup memory layout
  powerpc/8xx: CONFIG_PIN_TLB unneeded for CONFIG_PPC_EARLY_DEBUG_CPM
  powerpc/8xx: map 16M RAM at startup
  powerpc/8xx: move 8xx SPRN defines into reg_8xx.h and add some missing
    ones
  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

-- 
2.1.0

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