Hi, So this is a new version of the nohz cpusets based on 3.7, except it's not using cpusets anymore and I actually based it on the middle of the 3.8 merge window in order to get latest upstream full dynticks preparatory work: cputime cleanups, RCU user mode, context tracking subsystem, nohz code consolidation, ...
So the big changes since the last nohz cpuset release are: * printk now uses irq work so it doesn't rely on the tick anymore (provided your arch implements irq work with IPIs or alike). This chunk has been proposed for the 3.8 merge window: https://lkml.org/lkml/2012/12/17/177 May be Linus will pull, may be not. We'll see. In any case I've included it in this tree but I'm not reposting this part of the patchset to avoid spamming you. * cputime doesn't rely on IPIs anymore. Now the reader does a special computation to remotely get the tickless cputime. * No more cpusets interface. Paul McKenney suggested me to start with a boot time kernel parameter to define the full dynticks cpumask. And he was totally right, it makes the code much more simple. That's a good way to start and to make the mainlining easier. We can still add a runtime configuration later if necessary. * Now there is always a CPU handling the timekeeping. This can be further optimized and more power-friendly, I really did something simple-stupid. I guess we'll try to get that into a better shape with Hakan. But at least the timekeeping now works. * It uses the new RCU callbacks offlining feature. This way a full dynticks CPU doesn't need to keep the tick to handle local callbacks. This is still very experimental though. * No more specific IPI vector for full dynticks. We just use the scheduler ipi. The branch is: git://git.kernel.org/pub/scm/linux/kernel/git/frederic/linux-dynticks.git 3.7-nohz1 There is still quite some work to do. == How to use? == Select: CONFIG_NO_HZ CONFIG_RCU_USER_QS CONFIG_VIRT_CPU_ACCOUNTING_GEN CONFIG_RCU_NOCB_CPU CONFIG_NO_HZ_FULL You always need at least one timekeeping CPU. Let's imagine you have 4 CPUs. We keep the CPU 0 to offline RCU callbacks there and to handle the timekeeping. We set the rest as full dynticks. So you need the following kernel parameters: rcu_nocbs=1-3 full_nohz=1-3 (Note rcu_nocbs value must always be the same as full_nohz). Now if you want proper isolation you need to: * Migrate your processes adequately * Migrate your irqs to CPU 0 * Migrate the RCU nocb threads to CPU 0. Example with the above configuration: for p in $(ps -o pid= -C rcuo1,rcuo2,rcuo3) do taskset -cp 0 $p done Then run what you want on the full dynticks CPUs. For best results, run 1 task per CPU, mostly in userspace and mostly CPU bound (otherwise more IO = more kernel mode execution = more chances to get IPIs, tick restarted, workqueues, kthreads, etc...) This page contains a good reminder for those interested in CPU isolation: https://github.com/gby/linux/wiki But keep in mind that my tree is not yet ready for serious production. Happy Christmas, new year or whatever end of the world. --- Frederic Weisbecker (32): irq_work: Fix racy IRQ_WORK_BUSY flag setting irq_work: Fix racy check on work pending flag irq_work: Remove CONFIG_HAVE_IRQ_WORK nohz: Add API to check tick state irq_work: Don't stop the tick with pending works irq_work: Make self-IPIs optable printk: Wake up klogd using irq_work Merge branch 'nohz/printk-v8' into 3.7-nohz1-stage context_tracking: Add comments on interface and internals cputime: Generic on-demand virtual cputime accounting cputime: Allow dynamic switch between tick/virtual based cputime accounting cputime: Use accessors to read task cputime stats cputime: Safely read cputime of full dynticks CPUs nohz: Basic full dynticks interface nohz: Assign timekeeping duty to a non-full-nohz CPU nohz: Trace timekeeping update nohz: Wake up full dynticks CPUs when a timer gets enqueued rcu: Restart the tick on non-responding full dynticks CPUs sched: Comment on rq->clock correctness in ttwu_do_wakeup() in nohz sched: Update rq clock on nohz CPU before migrating tasks sched: Update rq clock on nohz CPU before setting fair group shares sched: Update rq clock on tickless CPUs before calling check_preempt_curr() sched: Update rq clock earlier in unthrottle_cfs_rq sched: Update clock of nohz busiest rq before balancing sched: Update rq clock before idle balancing sched: Update nohz rq clock before searching busiest group on load balancing nohz: Move nohz load balancer selection into idle logic nohz: Full dynticks mode nohz: Only stop the tick on RCU nocb CPUs nohz: Don't turn off the tick if rcu needs it nohz: Don't stop the tick if posix cpu timers are running nohz: Add some tracing Steven Rostedt (2): irq_work: Flush work on CPU_DYING irq_work: Warn if there's still work on cpu_down arch/alpha/Kconfig | 1 - arch/alpha/kernel/osf_sys.c | 6 +- arch/arm/Kconfig | 1 - arch/arm64/Kconfig | 1 - arch/blackfin/Kconfig | 1 - arch/frv/Kconfig | 1 - arch/hexagon/Kconfig | 1 - arch/mips/Kconfig | 1 - arch/parisc/Kconfig | 1 - arch/powerpc/Kconfig | 1 - arch/s390/Kconfig | 1 - arch/s390/kernel/vtime.c | 4 +- arch/sh/Kconfig | 1 - arch/sparc/Kconfig | 1 - arch/x86/Kconfig | 1 - arch/x86/kernel/apm_32.c | 11 +- drivers/isdn/mISDN/stack.c | 7 +- drivers/staging/iio/trigger/Kconfig | 1 - fs/binfmt_elf.c | 8 +- fs/binfmt_elf_fdpic.c | 7 +- include/asm-generic/cputime.h | 1 + include/linux/context_tracking.h | 28 +++++ include/linux/hardirq.h | 4 +- include/linux/init_task.h | 9 ++ include/linux/irq_work.h | 20 +++ include/linux/kernel_stat.h | 2 +- include/linux/posix-timers.h | 1 + include/linux/printk.h | 3 - include/linux/rcupdate.h | 8 ++ include/linux/sched.h | 48 +++++++- include/linux/tick.h | 26 ++++- include/linux/vtime.h | 47 +++++--- init/Kconfig | 22 +++- kernel/acct.c | 6 +- kernel/context_tracking.c | 91 +++++++++++---- kernel/cpu.c | 4 +- kernel/delayacct.c | 7 +- kernel/exit.c | 6 +- kernel/fork.c | 8 +- kernel/irq_work.c | 131 ++++++++++++++++----- kernel/posix-cpu-timers.c | 39 +++++- kernel/printk.c | 36 +++--- kernel/rcutree.c | 19 +++- kernel/rcutree_plugin.h | 13 +-- kernel/sched/core.c | 69 +++++++++++- kernel/sched/cputime.c | 222 ++++++++++++++++++++++++++++++----- kernel/sched/fair.c | 42 +++++++- kernel/sched/sched.h | 15 +++ kernel/signal.c | 12 ++- kernel/softirq.c | 11 +- kernel/time/Kconfig | 9 ++ kernel/time/tick-broadcast.c | 3 +- kernel/time/tick-common.c | 5 +- kernel/time/tick-sched.c | 142 ++++++++++++++++++++--- kernel/timer.c | 3 +- kernel/tsacct.c | 19 ++- 56 files changed, 955 insertions(+), 233 deletions(-) -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majord...@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
