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

[Lihao Liang]

On Sat, Jan 27, 2018 at 7:57 AM, Paul E. McKenney
<paulmck@xxxxxxxxxxxxxxxxxx> wrote:
> 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.
>

I should add that we also tested the normal synchronize_rcu() on the
same x86 machine, and the rcuperf figures were about 10 times slower
than those of synchronize_rcu_expedited().

Is this expected for synchronize_rcu()?

Best,
Lihao.

>                                                         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
>> >>
>> >
>>
>