Re: [PATCH RFC 00/16] A new RCU implementation based on a fast consensus protocol

From: Paul E. McKenney
Date: Sat Jan 27 2018 - 02:58:00 EST

On Sat, Jan 27, 2018 at 07:22:27AM +0000, Lihao Liang wrote:
> On Thu, Jan 25, 2018 at 5:53 AM, Paul E. McKenney
> <paulmck@xxxxxxxxxxxxxxxxxx> wrote:
> > On Tue, Jan 23, 2018 at 03:59:25PM +0800, lianglihao@xxxxxxxxxx wrote:
> >> From: Lihao Liang <lianglihao@xxxxxxxxxx>
> >>
> >> Dear Paul,
> >>
> >> This patch set implements a preemptive version of RCU (PRCU) based on the following paper:
> >>
> >> Fast Consensus Using Bounded Staleness for Scalable Read-mostly Synchronization.
> >> Haibo Chen, Heng Zhang, Ran Liu, Binyu Zang, and Haibing Guan.
> >> IEEE Transactions on Parallel and Distributed Systems (TPDS), 2016.
> >> https://dl.acm.org/citation.cfm?id=3024114.3024143
> >>
> >> We have also added preliminary callback-handling support. Thus, the current version
> >> provides APIs prcu_read_lock(), prcu_read_unlock(), synchronize_prcu(), call_prcu(),
> >> and prcu_barrier().
> >>
> >> This is an experimental patch, so it would be good to have some feedback.
> >>
> >> Known shortcoming is that the grace-period version is incremented in synchronize_prcu().
> >> If call_prcu() or prcu_barrier() is called but there is no synchronized_prcu() invoked,
> >> callbacks cannot be invoked. Later version should address this issue, e.g. adding a
> >> grace-period expedition mechanism. Others include to use a a hierarchical structure,
> >> taking into account the NUMA topology, to send IPI in synchronize_prcu().
> >>
> >> We have tested the implementation using rcutorture on both an x86 and ARM64 machine.
> >> PRCU passed 1h and 3h tests on all the newly added config files except PRCU07 reported BUG
> >> in a 1h run.
> >>
> >> [ 1593.604201] ---[ end trace b3bae911bec86152 ]---
> >> [ 1594.629450] prcu-torture:torture_onoff task: offlining 14
> >> [ 1594.755553] smpboot: CPU 14 is now offline
> >> [ 1594.757732] prcu-torture:torture_onoff task: offlined 14
> >> [ 1597.765149] prcu-torture:torture_onoff task: onlining 11
> >> [ 1597.766795] smpboot: Booting Node 0 Processor 11 APIC 0xb
> >> [ 1597.804102] prcu-torture:torture_onoff task: onlined 11
> >> [ 1599.365098] prcu-torture: rtc: ffffffffb0277b90 ver: 66358 tfle: 0 rta: 66358 rtaf: 0
> >> rtf: 66349 rtmbe: 0 rtbe: 1 rtbke: 0 rtbre: 0 rtbf: 0 rtb: 0 nt: 2233418
> >> onoff: 191/191:199/199 34,199:59,5102 10403:0 (HZ=1000) barrier: 188/189:1 cbflood: 225
> >> [ 1599.367946] prcu-torture: !!!
> >> [ 1599.367966] ------------[ cut here ]------------
> >
> > The "rtbe: 1" indicates that your implementation of prcu_barrier()
> > failed to wait for all preceding call_prcu() callbacks to be invoked.
> >
> > Does the immediately following "Reader Pipe:" list have any but the
> > first two numbers non-zero?
>
> Yes.

If the third or subsequent numbers are non-zero, that would indicate
too-short grace periods. This would be a critical bug in PRCU.

> >> We have also compared PRCU with TREE RCU using rcuperf with gp_exp set to true, that is
> >> synchronize_rcu_expedited was tested.
> >>
> >> The rcuperf results are as follows (average grace-period duration in ms of ten 10min runs):
> >>
> >> 16*Intel Xeon CPU@xxxxxx, 16GB memory, Ubuntu Linux 3.13.0-47-generic
> >>
> >> CPUs 2 4 8 12 15 16
> >> PRCU 0.14 1.07 4.15 8.02 10.79 15.16
> >> TREE 49.30 104.75 277.55 390.82 620.82 1381.54
> >>
> >> 64*Cortex-A72 CPU@xxxxxx, 130GB memory, Ubuntu Linux 4.10.0-21.23-generic
> >>
> >> CPUs 2 4 8 16 32 48 63 64
> >> PRCU 0.23 19.69 38.28 63.21 95.41 167.18 252.01 1841.44
> >> TREE 416.73 901.89 1060.86 743.00 920.66 1325.21 1646.20 23806.27
> >
> > Well, at the very least, this is a bug report on either expedited RCU
> > grace-period latency or on rcuperf's measurements, and thank you for that.
> > I will look into this. In the meantime, could you please let me know
> > exactly how you invoked rcuperf?
>
> We used the following command to invoke rcuperf:
>
> sudo ./kvm.sh --torture rcuperf --duration 10 --configs 10*TREE
>
> The actual script run-rcuperf.sh to run the experiments can be found
> in the following email of this patch series:
>
> [PATCH RFC 15/16] rcutorture: Add scripts to run experiments
>
> Please let us know how it goes.

Will do!

As I said before, at the very least you have identified a performance bug
in RCU expedited grace periods.

Thanx, Paul

> Many thanks,
> Lihao.
>
> > I have a few comments on some of your patches based on a quick scan
> > through them.
> >
> > Thanx, Paul
> >
> >> Best wishes,
> >> Lihao.
> >>
> >>
> >> Lihao Liang (15):
> >> rcutorture: Add PRCU rcu_torture_ops
> >> rcutorture: Add PRCU test config files
> >> rcuperf: Add PRCU rcu_perf_ops
> >> rcuperf: Add PRCU test config files
> >> rcuperf: Set gp_exp to true for tests to run
> >> prcu: Implement call_prcu() API
> >> prcu: Implement PRCU callback processing
> >> prcu: Implement prcu_barrier() API
> >> rcutorture: Test call_prcu() and prcu_barrier()
> >> rcutorture: Add basic ARM64 support to run scripts
> >> prcu: Add PRCU Kconfig parameter
> >> prcu: Comment source code
> >> rcuperf: Add config files with various CONFIG_NR_CPUS
> >> rcutorture: Add scripts to run experiments
> >> Add GPLv2 license
> >>
> >> Heng Zhang (1):
> >> prcu: Add PRCU implementation
> >>
> >> include/linux/interrupt.h | 3 +
> >> include/linux/prcu.h | 122 +++++
> >> include/linux/rcupdate.h | 1 +
> >> init/Kconfig | 7 +
> >> init/main.c | 2 +
> >> kernel/rcu/Makefile | 1 +
> >> kernel/rcu/prcu.c | 497 +++++++++++++++++++++
> >> kernel/rcu/rcuperf.c | 33 +-
> >> kernel/rcu/rcutorture.c | 40 +-
> >> kernel/rcu/tree.c | 1 +
> >> kernel/sched/core.c | 2 +
> >> kernel/time/timer.c | 2 +
> >> kvm.sh | 452 +++++++++++++++++++
> >> run-rcuperf.sh | 26 ++
> >> .../testing/selftests/rcutorture/bin/functions.sh | 17 +-
> >> .../selftests/rcutorture/configs/rcu/CFLIST | 5 +
> >> .../selftests/rcutorture/configs/rcu/PRCU02 | 27 ++
> >> .../selftests/rcutorture/configs/rcu/PRCU02.boot | 1 +
> >> .../selftests/rcutorture/configs/rcu/PRCU03 | 23 +
> >> .../selftests/rcutorture/configs/rcu/PRCU03.boot | 2 +
> >> .../selftests/rcutorture/configs/rcu/PRCU06 | 26 ++
> >> .../selftests/rcutorture/configs/rcu/PRCU06.boot | 5 +
> >> .../selftests/rcutorture/configs/rcu/PRCU07 | 25 ++
> >> .../selftests/rcutorture/configs/rcu/PRCU07.boot | 2 +
> >> .../selftests/rcutorture/configs/rcu/PRCU09 | 19 +
> >> .../selftests/rcutorture/configs/rcu/PRCU09.boot | 1 +
> >> .../selftests/rcutorture/configs/rcuperf/CFLIST | 1 +
> >> .../selftests/rcutorture/configs/rcuperf/PRCU | 20 +
> >> .../selftests/rcutorture/configs/rcuperf/PRCU-12 | 21 +
> >> .../rcutorture/configs/rcuperf/PRCU-12.boot | 1 +
> >> .../selftests/rcutorture/configs/rcuperf/PRCU-14 | 21 +
> >> .../rcutorture/configs/rcuperf/PRCU-14.boot | 1 +
> >> .../selftests/rcutorture/configs/rcuperf/PRCU-15 | 21 +
> >> .../rcutorture/configs/rcuperf/PRCU-15.boot | 1 +
> >> .../selftests/rcutorture/configs/rcuperf/PRCU-16 | 21 +
> >> .../rcutorture/configs/rcuperf/PRCU-16.boot | 1 +
> >> .../selftests/rcutorture/configs/rcuperf/PRCU-2 | 21 +
> >> .../rcutorture/configs/rcuperf/PRCU-2.boot | 1 +
> >> .../selftests/rcutorture/configs/rcuperf/PRCU-32 | 21 +
> >> .../rcutorture/configs/rcuperf/PRCU-32.boot | 1 +
> >> .../selftests/rcutorture/configs/rcuperf/PRCU-4 | 21 +
> >> .../rcutorture/configs/rcuperf/PRCU-4.boot | 1 +
> >> .../selftests/rcutorture/configs/rcuperf/PRCU-48 | 21 +
> >> .../rcutorture/configs/rcuperf/PRCU-48.boot | 1 +
> >> .../selftests/rcutorture/configs/rcuperf/PRCU-56 | 21 +
> >> .../rcutorture/configs/rcuperf/PRCU-56.boot | 1 +
> >> .../selftests/rcutorture/configs/rcuperf/PRCU-60 | 21 +
> >> .../rcutorture/configs/rcuperf/PRCU-60.boot | 1 +
> >> .../selftests/rcutorture/configs/rcuperf/PRCU-62 | 21 +
> >> .../rcutorture/configs/rcuperf/PRCU-62.boot | 1 +
> >> .../selftests/rcutorture/configs/rcuperf/PRCU-64 | 21 +
> >> .../rcutorture/configs/rcuperf/PRCU-64.boot | 1 +
> >> .../selftests/rcutorture/configs/rcuperf/PRCU-8 | 21 +
> >> .../rcutorture/configs/rcuperf/PRCU-8.boot | 1 +
> >> .../selftests/rcutorture/configs/rcuperf/PRCU.boot | 1 +
> >> .../selftests/rcutorture/configs/rcuperf/TREE-12 | 21 +
> >> .../selftests/rcutorture/configs/rcuperf/TREE-14 | 21 +
> >> .../selftests/rcutorture/configs/rcuperf/TREE-15 | 21 +
> >> .../selftests/rcutorture/configs/rcuperf/TREE-16 | 21 +
> >> .../selftests/rcutorture/configs/rcuperf/TREE-2 | 21 +
> >> .../selftests/rcutorture/configs/rcuperf/TREE-32 | 21 +
> >> .../selftests/rcutorture/configs/rcuperf/TREE-4 | 21 +
> >> .../selftests/rcutorture/configs/rcuperf/TREE-48 | 21 +
> >> .../selftests/rcutorture/configs/rcuperf/TREE-56 | 21 +
> >> .../selftests/rcutorture/configs/rcuperf/TREE-60 | 21 +
> >> .../selftests/rcutorture/configs/rcuperf/TREE-62 | 21 +
> >> .../selftests/rcutorture/configs/rcuperf/TREE-64 | 21 +
> >> .../selftests/rcutorture/configs/rcuperf/TREE-8 | 21 +
> >> 68 files changed, 1918 insertions(+), 5 deletions(-)
> >> create mode 100644 include/linux/prcu.h
> >> create mode 100644 kernel/rcu/prcu.c
> >> create mode 100755 kvm.sh
> >> create mode 100755 run-rcuperf.sh
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/PRCU02
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/PRCU02.boot
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/PRCU03
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/PRCU03.boot
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/PRCU06
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/PRCU06.boot
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/PRCU07
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/PRCU07.boot
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/PRCU09
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcu/PRCU09.boot
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/PRCU
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/PRCU-12
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/PRCU-12.boot
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/PRCU-14
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/PRCU-14.boot
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/PRCU-15
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/PRCU-15.boot
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/PRCU-16
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/PRCU-16.boot
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/PRCU-2
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/PRCU-2.boot
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/PRCU-32
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/PRCU-32.boot
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/PRCU-4
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/PRCU-4.boot
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/PRCU-48
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/PRCU-48.boot
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/PRCU-56
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/PRCU-56.boot
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/PRCU-60
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/PRCU-60.boot
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/PRCU-62
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/PRCU-62.boot
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/PRCU-64
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/PRCU-64.boot
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/PRCU-8
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/PRCU-8.boot
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/PRCU.boot
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/TREE-12
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/TREE-14
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/TREE-15
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/TREE-16
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/TREE-2
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/TREE-32
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/TREE-4
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/TREE-48
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/TREE-56
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/TREE-60
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/TREE-62
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/TREE-64
> >> create mode 100644 tools/testing/selftests/rcutorture/configs/rcuperf/TREE-8
> >>
> >> --
> >> 2.14.1.729.g59c0ea183
> >>
> >
>