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    Subject[RFC PATCH v2 00/10] powerpc/32: switch VDSO to C implementation.
    Date
    This is a second tentative to switch powerpc/32 vdso to generic C implementation.

    It will likely not work on 64 bits or even build properly at the moment.

    powerpc is a bit special for VDSO as well as system calls in the
    way that it requires setting CR SO bit which cannot be done in C.
    Therefore, entry/exit and fallback needs to be performed in ASM.

    To allow that, the fallback calls are moved out of the common code
    and left to the arches.

    A few other changes in the common code have allowed performance improvement.

    The performance has improved since first RFC, but it is still lower than
    current assembly VDSO.

    On a powerpc8xx, with current powerpc/32 ASM VDSO:

    gettimeofday: vdso: 737 nsec/call
    clock-getres-realtime: vdso: 475 nsec/call
    clock-gettime-realtime: vdso: 892 nsec/call
    clock-getres-monotonic: vdso: 475 nsec/call
    clock-gettime-monotonic: vdso: 1014 nsec/call

    First try of C implementation:

    gettimeofday: vdso: 1533 nsec/call
    clock-getres-realtime: vdso: 853 nsec/call
    clock-gettime-realtime: vdso: 1570 nsec/call
    clock-getres-monotonic: vdso: 835 nsec/call
    clock-gettime-monotonic: vdso: 1605 nsec/call

    With this series:

    gettimeofday: vdso: 1016 nsec/call
    clock-getres-realtime: vdso: 560 nsec/call
    clock-gettime-realtime: vdso: 1192 nsec/call
    clock-getres-monotonic: vdso: 560 nsec/call
    clock-gettime-monotonic: vdso: 1192 nsec/call


    Changes made to other arches are untested, not even compiled.


    Christophe Leroy (10):
    lib: vdso: ensure all arches have 32bit fallback
    lib: vdso: move call to fallback out of common code.
    lib: vdso: Change __cvdso_clock_gettime/getres_common() to
    __cvdso_clock_gettime/getres()
    lib: vdso: get pointer to vdso data from the arch
    lib: vdso: inline do_hres()
    lib: vdso: make do_coarse() return 0
    lib: vdso: don't use READ_ONCE() in __c_kernel_time()
    lib: vdso: Avoid duplication in __cvdso_clock_getres()
    powerpc/vdso32: inline __get_datapage()
    powerpc/32: Switch VDSO to C implementation.

    arch/arm/include/asm/vdso/gettimeofday.h | 26 +++
    arch/arm/vdso/vgettimeofday.c | 32 ++-
    arch/arm64/include/asm/vdso/compat_gettimeofday.h | 2 -
    arch/arm64/include/asm/vdso/gettimeofday.h | 26 +++
    arch/arm64/kernel/vdso/vgettimeofday.c | 24 +-
    arch/arm64/kernel/vdso32/vgettimeofday.c | 39 +++-
    arch/mips/include/asm/vdso/gettimeofday.h | 28 ++-
    arch/mips/vdso/vgettimeofday.c | 56 ++++-
    arch/powerpc/Kconfig | 2 +
    arch/powerpc/include/asm/vdso/gettimeofday.h | 45 ++++
    arch/powerpc/include/asm/vdso/vsyscall.h | 27 +++
    arch/powerpc/include/asm/vdso_datapage.h | 28 +--
    arch/powerpc/kernel/asm-offsets.c | 23 +-
    arch/powerpc/kernel/time.c | 92 +-------
    arch/powerpc/kernel/vdso.c | 19 +-
    arch/powerpc/kernel/vdso32/Makefile | 19 +-
    arch/powerpc/kernel/vdso32/cacheflush.S | 9 +-
    arch/powerpc/kernel/vdso32/datapage.S | 28 +--
    arch/powerpc/kernel/vdso32/gettimeofday.S | 265 +++-------------------
    arch/powerpc/kernel/vdso32/vgettimeofday.c | 32 +++
    arch/x86/entry/vdso/vclock_gettime.c | 52 ++++-
    arch/x86/include/asm/vdso/gettimeofday.h | 28 ++-
    lib/vdso/gettimeofday.c | 100 +++-----
    23 files changed, 505 insertions(+), 497 deletions(-)
    create mode 100644 arch/powerpc/include/asm/vdso/gettimeofday.h
    create mode 100644 arch/powerpc/include/asm/vdso/vsyscall.h
    create mode 100644 arch/powerpc/kernel/vdso32/vgettimeofday.c

    --
    2.13.3

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