Messages in this thread | | | Date | Tue, 25 Apr 2017 15:36:42 -0700 | From | "Paul E. McKenney" <> | Subject | Re: TREE_SRCU slows hotplug by factor ~16 |
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On Mon, Apr 24, 2017 at 09:24:42AM -0700, Paul E. McKenney wrote: > On Mon, Apr 24, 2017 at 09:35:03AM +0200, Mike Galbraith wrote: > > On Sun, 2017-04-23 at 23:22 -0700, Paul E. McKenney wrote: > > > > > Could you please collect an ftrace (or whatever) showing the timestamp > > > sequence of calls to synchronize_srcu(), synchronize_srcu_expedited(), > > > and call_srcu() during the execution of the stress script? If it is easy > > > to do, also the timestamp sequence of returns from synchronize_srcu() > > > and synchronize_srcu_expedited()? > > > > The first two minutes below config bits, trace_printk([enter/exit]) in > > each function. If you (unlikely, but..) want the whole trace, holler. > > > > # RCU Subsystem > > CONFIG_TREE_RCU=y > > CONFIG_RCU_EXPERT=y > > CONFIG_SRCU=y > > # CONFIG_CLASSIC_SRCU is not set > > CONFIG_TREE_SRCU=y > > # CONFIG_TASKS_RCU is not set > > CONFIG_RCU_STALL_COMMON=y > > CONFIG_RCU_FANOUT=64 > > CONFIG_RCU_FANOUT_LEAF=16 > > # CONFIG_RCU_FAST_NO_HZ is not set > > # CONFIG_TREE_RCU_TRACE is not set > > CONFIG_RCU_KTHREAD_PRIO=0 > > CONFIG_RCU_NOCB_CPU=y > > CONFIG_RCU_NOCB_CPU_NONE=y > > # CONFIG_RCU_NOCB_CPU_ZERO is not set > > # CONFIG_RCU_NOCB_CPU_ALL is not set > > # RCU Debugging > > # CONFIG_PROVE_RCU is not set > > # CONFIG_SPARSE_RCU_POINTER is not set > > # CONFIG_RCU_PERF_TEST is not set > > # CONFIG_RCU_TORTURE_TEST is not set > > CONFIG_RCU_CPU_STALL_TIMEOUT=60 > > # CONFIG_RCU_TRACE is not set > > # CONFIG_RCU_EQS_DEBUG is not set > > Thank you for the data, extremely helpful! I now know that I must > immediately fix this the hard way rather than trying several simpler > possibilities that, according to your trace data, would be complete > wastes of time. > > My initial calculation was actually optimistic. There was one > exit-to-enter interval at about 80 milliseconds, but the second > longest is 342 microseconds, and the vast majority are under 200 > microseconds. > > Back to the drawing board! > > This will take some time, but I should have a patch for you in a few days, > hopefully sooner.
Making progress, might have something late tomorrow (Wednesday) Pacific Time, will definitely have something Thursday Pacific Time.
Thanx, Paul
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