Re: [RFC PATCH v3 0/5] powerpc: Support context tracking for Power pSeries
On Mon, May 13, 2013 at 04:03:13PM +0800, Li Zhong wrote: On Mon, 2013-05-13 at 15:51 +1000, Benjamin Herrenschmidt wrote: On Mon, 2013-05-13 at 13:21 +0800, Li Zhong wrote: These patches try to support context tracking for Power arch, beginning with 64-bit pSeries. The codes are ported from that of the x86_64, and in each patch, I listed the corresponding patch for x86. So that's yet another pile of bloat on all syscall entry/exit and exception entry/exit. What is it used for ? (I haven't followed on x86_64 side). To my understanding, it is used to enable RCU user extended quiescent state, so RCU on that cpu doesn't need scheduler ticks. And together with some other code(already in 3.10), we are able to remove the ticks in some cases (e.g. only 1 task running on the cpu, with some other limitations). Maybe Paul, or Frederic could give some better descriptions. That's pretty much it. It helps RCU and cputime accounting infrastructure to know when we enter/exit userspace. This way we can: * Consider the CPU as idle from an RCU point of view when we run in userspace, so RCU won't need the tick to stay alive. * Account cputime (utime/stime/...) without using the tick. Ok powerpc already has CONFIG_VIRT_CPU_ACCOUNTING_NATIVE but making it working with full dynticks would require some tweaks. All in one this is to support full dynticks. Thanks. ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: [RFC PATCH v3 0/5] powerpc: Support context tracking for Power pSeries
On Mon, May 13, 2013 at 06:59:23PM +1000, Benjamin Herrenschmidt wrote: On Mon, 2013-05-13 at 16:03 +0800, Li Zhong wrote: To my understanding, it is used to enable RCU user extended quiescent state, so RCU on that cpu doesn't need scheduler ticks. And together with some other code(already in 3.10), we are able to remove the ticks in some cases (e.g. only 1 task running on the cpu, with some other limitations). Ok, sounds interesting. Once you fix the little cosmetic issue, I don't see any reason not to merge them as it's basically wiring up an existing feature (in that regard the patches are pretty straightforward) and I assume the overhead is only there when you enable it. Yeah when CONFIG_RCU_USER_QS=n and CONFIG_VIRT_CPU_ACCOUNTING_GEN=n this should be zero overhead. And those configs are only needed for full dynticks. Thanks. Cheers, Ben. ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: [RFC PATCH v3 0/5] powerpc: Support context tracking for Power pSeries
On Mon, 2013-05-13 at 15:51 +1000, Benjamin Herrenschmidt wrote: On Mon, 2013-05-13 at 13:21 +0800, Li Zhong wrote: These patches try to support context tracking for Power arch, beginning with 64-bit pSeries. The codes are ported from that of the x86_64, and in each patch, I listed the corresponding patch for x86. So that's yet another pile of bloat on all syscall entry/exit and exception entry/exit. What is it used for ? (I haven't followed on x86_64 side). To my understanding, it is used to enable RCU user extended quiescent state, so RCU on that cpu doesn't need scheduler ticks. And together with some other code(already in 3.10), we are able to remove the ticks in some cases (e.g. only 1 task running on the cpu, with some other limitations). Maybe Paul, or Frederic could give some better descriptions. Thanks, Zhong Cheers, Ben. v3: This version is mainly a rebasing, against 3.10-rc1, also as the common code to handle the exception are pulled into 3.10, so there is no dependency on tip tree. So patch #2 and #6 in previous version_2 is merged together. Li Zhong (5): powerpc: Syscall hooks for context tracking subsystem powerpc: Exception hooks for context tracking subsystem powerpc: Exit user context on notify resume powerpc: Use the new schedule_user API on userspace preemption powerpc: select HAVE_CONTEXT_TRACKING for pSeries arch/powerpc/include/asm/context_tracking.h | 10 +++ arch/powerpc/include/asm/thread_info.h |7 ++- arch/powerpc/kernel/entry_64.S |3 +- arch/powerpc/kernel/ptrace.c|5 ++ arch/powerpc/kernel/signal.c|5 ++ arch/powerpc/kernel/traps.c | 91 --- arch/powerpc/mm/fault.c | 16 - arch/powerpc/mm/hash_utils_64.c | 38 --- arch/powerpc/platforms/pseries/Kconfig |1 + 9 files changed, 140 insertions(+), 36 deletions(-) create mode 100644 arch/powerpc/include/asm/context_tracking.h ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: [RFC PATCH v3 0/5] powerpc: Support context tracking for Power pSeries
On Mon, 2013-05-13 at 16:03 +0800, Li Zhong wrote: To my understanding, it is used to enable RCU user extended quiescent state, so RCU on that cpu doesn't need scheduler ticks. And together with some other code(already in 3.10), we are able to remove the ticks in some cases (e.g. only 1 task running on the cpu, with some other limitations). Ok, sounds interesting. Once you fix the little cosmetic issue, I don't see any reason not to merge them as it's basically wiring up an existing feature (in that regard the patches are pretty straightforward) and I assume the overhead is only there when you enable it. Cheers, Ben. ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: [RFC PATCH v3 0/5] powerpc: Support context tracking for Power pSeries
On Mon, 2013-05-13 at 18:59 +1000, Benjamin Herrenschmidt wrote: On Mon, 2013-05-13 at 16:03 +0800, Li Zhong wrote: To my understanding, it is used to enable RCU user extended quiescent state, so RCU on that cpu doesn't need scheduler ticks. And together with some other code(already in 3.10), we are able to remove the ticks in some cases (e.g. only 1 task running on the cpu, with some other limitations). Ok, sounds interesting. Once you fix the little cosmetic issue, I don't see any reason not to merge them as it's basically wiring up an existing feature (in that regard the patches are pretty straightforward) and I assume the overhead is only there when you enable it. Thanks for your support, Ben. Yes, there should be no overhead if not enabled. Thanks, Zhong Cheers, Ben. ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
[RFC PATCH v3 0/5] powerpc: Support context tracking for Power pSeries
These patches try to support context tracking for Power arch, beginning with 64-bit pSeries. The codes are ported from that of the x86_64, and in each patch, I listed the corresponding patch for x86. v3: This version is mainly a rebasing, against 3.10-rc1, also as the common code to handle the exception are pulled into 3.10, so there is no dependency on tip tree. So patch #2 and #6 in previous version_2 is merged together. Li Zhong (5): powerpc: Syscall hooks for context tracking subsystem powerpc: Exception hooks for context tracking subsystem powerpc: Exit user context on notify resume powerpc: Use the new schedule_user API on userspace preemption powerpc: select HAVE_CONTEXT_TRACKING for pSeries arch/powerpc/include/asm/context_tracking.h | 10 +++ arch/powerpc/include/asm/thread_info.h |7 ++- arch/powerpc/kernel/entry_64.S |3 +- arch/powerpc/kernel/ptrace.c|5 ++ arch/powerpc/kernel/signal.c|5 ++ arch/powerpc/kernel/traps.c | 91 --- arch/powerpc/mm/fault.c | 16 - arch/powerpc/mm/hash_utils_64.c | 38 --- arch/powerpc/platforms/pseries/Kconfig |1 + 9 files changed, 140 insertions(+), 36 deletions(-) create mode 100644 arch/powerpc/include/asm/context_tracking.h -- 1.7.9.5 ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
Re: [RFC PATCH v3 0/5] powerpc: Support context tracking for Power pSeries
On Mon, 2013-05-13 at 13:21 +0800, Li Zhong wrote: These patches try to support context tracking for Power arch, beginning with 64-bit pSeries. The codes are ported from that of the x86_64, and in each patch, I listed the corresponding patch for x86. So that's yet another pile of bloat on all syscall entry/exit and exception entry/exit. What is it used for ? (I haven't followed on x86_64 side). Cheers, Ben. v3: This version is mainly a rebasing, against 3.10-rc1, also as the common code to handle the exception are pulled into 3.10, so there is no dependency on tip tree. So patch #2 and #6 in previous version_2 is merged together. Li Zhong (5): powerpc: Syscall hooks for context tracking subsystem powerpc: Exception hooks for context tracking subsystem powerpc: Exit user context on notify resume powerpc: Use the new schedule_user API on userspace preemption powerpc: select HAVE_CONTEXT_TRACKING for pSeries arch/powerpc/include/asm/context_tracking.h | 10 +++ arch/powerpc/include/asm/thread_info.h |7 ++- arch/powerpc/kernel/entry_64.S |3 +- arch/powerpc/kernel/ptrace.c|5 ++ arch/powerpc/kernel/signal.c|5 ++ arch/powerpc/kernel/traps.c | 91 --- arch/powerpc/mm/fault.c | 16 - arch/powerpc/mm/hash_utils_64.c | 38 --- arch/powerpc/platforms/pseries/Kconfig |1 + 9 files changed, 140 insertions(+), 36 deletions(-) create mode 100644 arch/powerpc/include/asm/context_tracking.h ___ Linuxppc-dev mailing list Linuxppc-dev@lists.ozlabs.org https://lists.ozlabs.org/listinfo/linuxppc-dev
