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Date: Sat, 27 Jan 2018 09:57:03 +0000
From: Lihao Liang <lihao.liang@...il.com>
To: Paul McKenney <paulmck@...ux.vnet.ibm.com>
Cc: "Guohanjun (Hanjun Guo)" <guohanjun@...wei.com>, heng.z@...wei.com,
hb.chen@...wei.com, linux-kernel@...r.kernel.org
Subject: Re: [PATCH RFC 00/16] A new RCU implementation based on a fast
consensus protocol
On Sat, Jan 27, 2018 at 7:57 AM, Paul E. McKenney
<paulmck@...ux.vnet.ibm.com> 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@...ux.vnet.ibm.com> wrote:
>> > On Tue, Jan 23, 2018 at 03:59:25PM +0800, lianglihao@...wei.com wrote:
>> >> From: Lihao Liang <lianglihao@...wei.com>
>> >>
>> >> 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@...GHz, 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@...GHz, 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
>> >>
>> >
>>
>
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