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Date: Fri, 14 Sep 2012 21:05:27 -0400 From: John Stultz <john.stultz@...aro.org> To: linux-kernel@...r.kernel.org Cc: John Stultz <john.stultz@...aro.org>, Catalin Marinas <catalin.marinas@....com>, Arnd Bergmann <arnd@...db.de>, Richard Cochran <richardcochran@...il.com>, Prarit Bhargava <prarit@...hat.com>, Thomas Gleixner <tglx@...utronix.de> Subject: [PATCH 0/3] Remove jiffies clocksource's dependency on CLOCK_TICK_RATE Just wanted to send this out for initial review and comments. During Linux Plumbers, Thomas mentioned that Arnd was still wanting to kill off the derived values from the compile time constant CLOCK_TICK_RATE, as it is a problem for unified zImage on ARM. One issue holding this back is that CLOCK_TICK_RATE allows us to address the granularity error of the underlying timer hardware, allowing for accurate timekeeping with jiffies and jiffies derived clocksources. Thomas proposed allowing the jiffies correction to be done dynamically at runtime, and this is my first attempt at such an approach. * The first patch is a simple cleanup of an unused define. * The second patch adds the hook to add a refined jiffies clocksource, and kills the values derived at compile time from CLOCK_TICK_RATE. * The third is a patch that adds the refined jiffies registration to all arches. Clearly, since in most cases platforms aren't using jiffies as a clocksource (except for just briefly in early boot), its quality doesn't matter that much. So I'd rather not actually submit the third patch, which adds unnecessary code in most cases, and instead allow architectures to add their portion as they see fit/regressions. I've only done some initial testing, and haven't tested with all HZ values yet, so there may still be issues, but its looking reasonably good so far. Anyway, I'd appreciate any feedback on this approach, or suggestions for other ways to allow for dynamic adjustments at runtime. thanks -john Cc: Catalin Marinas <catalin.marinas@....com> Cc: Arnd Bergmann <arnd@...db.de> Cc: Richard Cochran <richardcochran@...il.com> Cc: Prarit Bhargava <prarit@...hat.com> Cc: Thomas Gleixner <tglx@...utronix.de> John Stultz (3): jiffies: Kill unused TICK_USEC_TO_NSEC jiffies: Remove compile time assumptions about CLOCK_TICK_RATE jiffies: Add register_refined_jiffies() call to every arch arch/alpha/kernel/setup.c | 3 +++ arch/arm/kernel/setup.c | 2 ++ arch/avr32/kernel/setup.c | 2 ++ arch/blackfin/kernel/setup.c | 2 ++ arch/c6x/kernel/setup.c | 2 ++ arch/cris/kernel/setup.c | 2 ++ arch/h8300/kernel/setup.c | 2 ++ arch/hexagon/kernel/setup.c | 2 ++ arch/ia64/kernel/setup.c | 2 ++ arch/m32r/kernel/setup.c | 2 ++ arch/m68k/kernel/setup_mm.c | 2 ++ arch/m68k/kernel/setup_no.c | 2 ++ arch/microblaze/kernel/setup.c | 2 ++ arch/mips/kernel/setup.c | 2 ++ arch/mn10300/kernel/setup.c | 2 ++ arch/openrisc/kernel/setup.c | 2 ++ arch/parisc/kernel/setup.c | 3 ++- arch/powerpc/kernel/setup_32.c | 2 ++ arch/powerpc/kernel/setup_64.c | 2 ++ arch/s390/kernel/setup.c | 2 ++ arch/score/kernel/setup.c | 2 ++ arch/sh/kernel/setup.c | 2 ++ arch/sparc/kernel/setup_32.c | 2 ++ arch/sparc/kernel/setup_64.c | 2 ++ arch/tile/kernel/setup.c | 2 ++ arch/um/kernel/um_arch.c | 2 ++ arch/unicore32/kernel/setup.c | 2 ++ arch/x86/kernel/setup.c | 3 +++ arch/xtensa/kernel/setup.c | 3 ++- include/linux/jiffies.h | 21 ++------------------- kernel/time/jiffies.c | 32 +++++++++++++++++++++++++++++++- 31 files changed, 93 insertions(+), 22 deletions(-) -- 1.7.9.5 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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