[PATCH V12 00/14] riscv: Add Native/Paravirt qspinlock support

From: guoren
Date: Mon Dec 25 2023 - 07:59:16 EST

From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>

patch[1 - 8]: Native qspinlock
patch[9 -14]: Paravirt qspinlock

This series based on:
- v6.7-rc7
- Rework & improve riscv cmpxchg.h and atomic.h
https://lore.kernel.org/linux-riscv/20230810040349.92279-2-leobras@xxxxxxxxxx/

You can directly try it:
https://github.com/guoren83/linux/tree/qspinlock_v12

Native qspinlock
================

This time we've proved the qspinlock on th1520 [1] & sg2042 [2], which
gives stability and performance improvement. All T-HEAD processors have
a strong LR/SC forward progress guarantee than the requirements of the
ISA, which could satisfy the xchg_tail of native_qspinlock. Now,
qspinlock has been run with us for more than 1 year, and we have enough
confidence to enable it for all the T-HEAD processors. Of causes, we
found a livelock problem with the qspinlock lock torture test from the
CPU store merge buffer delay mechanism, which caused the queued spinlock
becomes a dead ring and RCU warning to come out. We introduce a custom
WRITE_ONCE to solve this, which will be fixed in the next generation of
hardware.

We've tested the patch on SOPHGO sg2042 & th1520 and passed the stress
test on Fedora & Ubuntu & OpenEuler ... Here is the performance
comparison between qspinlock and ticket_lock on sg2042 (64 cores):

sysbench test=threads threads=32 yields=100 lock=8 (+13.8%):
queued_spinlock 0.5109/0.00
ticket_spinlock 0.5814/0.00

perf futex/hash (+6.7%):
queued_spinlock 1444393 operations/sec (+- 0.09%)
ticket_spinlock 1353215 operations/sec (+- 0.15%)

perf futex/wake-parallel (+8.6%):
queued_spinlock (waking 1/64 threads) in 0.0253 ms (+-2.90%)
ticket_spinlock (waking 1/64 threads) in 0.0275 ms (+-3.12%)

perf futex/requeue (+4.2%):
queued_spinlock Requeued 64 of 64 threads in 0.0785 ms (+-0.55%)
ticket_spinlock Requeued 64 of 64 threads in 0.0818 ms (+-4.12%)


System Benchmarks (+6.4%)
queued_spinlock:
System Benchmarks Index Values BASELINE RESULT INDEX
Dhrystone 2 using register variables 116700.0 628613745.4 53865.8
Double-Precision Whetstone 55.0 182422.8 33167.8
Execl Throughput 43.0 13116.6 3050.4
File Copy 1024 bufsize 2000 maxblocks 3960.0 7762306.2 19601.8
File Copy 256 bufsize 500 maxblocks 1655.0 3417556.8 20649.9
File Copy 4096 bufsize 8000 maxblocks 5800.0 7427995.7 12806.9
Pipe Throughput 12440.0 23058600.5 18535.9
Pipe-based Context Switching 4000.0 2835617.7 7089.0
Process Creation 126.0 12537.3 995.0
Shell Scripts (1 concurrent) 42.4 57057.4 13456.9
Shell Scripts (8 concurrent) 6.0 7367.1 12278.5
System Call Overhead 15000.0 33308301.3 22205.5
========
System Benchmarks Index Score 12426.1

ticket_spinlock:
System Benchmarks Index Values BASELINE RESULT INDEX
Dhrystone 2 using register variables 116700.0 626541701.9 53688.2
Double-Precision Whetstone 55.0 181921.0 33076.5
Execl Throughput 43.0 12625.1 2936.1
File Copy 1024 bufsize 2000 maxblocks 3960.0 6553792.9 16550.0
File Copy 256 bufsize 500 maxblocks 1655.0 3189231.6 19270.3
File Copy 4096 bufsize 8000 maxblocks 5800.0 7221277.0 12450.5
Pipe Throughput 12440.0 20594018.7 16554.7
Pipe-based Context Switching 4000.0 2571117.7 6427.8
Process Creation 126.0 10798.4 857.0
Shell Scripts (1 concurrent) 42.4 57227.5 13497.1
Shell Scripts (8 concurrent) 6.0 7329.2 12215.3
System Call Overhead 15000.0 30766778.4 20511.2
========
System Benchmarks Index Score 11670.7

The qspinlock has a significant improvement on SOPHGO SG2042 64
cores platform than the ticket_lock.

Paravirt qspinlock
==================

We implemented kvm_kick_cpu/kvm_wait_cpu and add tracepoints to observe
the behaviors and introduce a new SBI extension SBI_EXT_PVLOCK.

Changlog:
V12:
- Remove force thead qspinlock with errata
- Separate Zicbop patch from this series
- Remove cpus >= 16 patch
- Cleanup rebase and move it on v6.7-rc7
- Reorder the coding struct with the last version's advice.

V11:
https://lore.kernel.org/linux-riscv/20230910082911.3378782-1-guoren@xxxxxxxxxx/
- Based on Leonardo Bras's cmpxchg_small patches v5.
- Based on Guo Ren's Optimize arch_spin_value_unlocked patch v3.
- Remove abusing alternative framework and use jump_label instead.
- Introduce prefetch.w to improve T-HEAD processors' LR/SC forward
progress guarantee.
- Optimize qspinlock xchg_tail when NR_CPUS >= 16K.

V10:
https://lore.kernel.org/linux-riscv/20230802164701.192791-1-guoren@xxxxxxxxxx/
- Using an alternative framework instead of static_key_branch in the
asm/spinlock.h.
- Fixup store merge buffer problem, which causes qspinlock lock
torture test livelock.
- Add paravirt qspinlock support, include KVM backend
- Add Compact NUMA-awared qspinlock support

V9:
https://lore.kernel.org/linux-riscv/20220808071318.3335746-1-guoren@xxxxxxxxxx/
- Cleanup generic ticket-lock code, (Using smp_mb__after_spinlock as
RCsc)
- Add qspinlock and combo-lock for riscv
- Add qspinlock to openrisc
- Use generic header in csky
- Optimize cmpxchg & atomic code

V8:
https://lore.kernel.org/linux-riscv/20220724122517.1019187-1-guoren@xxxxxxxxxx/
- Coding convention ticket fixup
- Move combo spinlock into riscv and simply asm-generic/spinlock.h
- Fixup xchg16 with wrong return value
- Add csky qspinlock
- Add combo & qspinlock & ticket-lock comparison
- Clean up unnecessary riscv acquire and release definitions
- Enable ARCH_INLINE_READ*/WRITE*/SPIN* for riscv & csky

V7:
https://lore.kernel.org/linux-riscv/20220628081946.1999419-1-guoren@xxxxxxxxxx/
- Add combo spinlock (ticket & queued) support
- Rename ticket_spinlock.h
- Remove unnecessary atomic_read in ticket_spin_value_unlocked

V6:
https://lore.kernel.org/linux-riscv/20220621144920.2945595-1-guoren@xxxxxxxxxx/
- Fixup Clang compile problem Reported-by: kernel test robot
- Cleanup asm-generic/spinlock.h
- Remove changelog in patch main comment part, suggested by
Conor.Dooley
- Remove "default y if NUMA" in Kconfig

V5:
https://lore.kernel.org/linux-riscv/20220620155404.1968739-1-guoren@xxxxxxxxxx/
- Update comment with RISC-V forward guarantee feature.
- Back to V3 direction and optimize asm code.

V4:
https://lore.kernel.org/linux-riscv/1616868399-82848-4-git-send-email-guoren@xxxxxxxxxx/
- Remove custom sub-word xchg implementation
- Add ARCH_USE_QUEUED_SPINLOCKS_XCHG32 in locking/qspinlock

V3:
https://lore.kernel.org/linux-riscv/1616658937-82063-1-git-send-email-guoren@xxxxxxxxxx/
- Coding convention by Peter Zijlstra's advices

V2:
https://lore.kernel.org/linux-riscv/1606225437-22948-2-git-send-email-guoren@xxxxxxxxxx/
- Coding convention in cmpxchg.h
- Re-implement short xchg
- Remove char & cmpxchg implementations

V1:
https://lore.kernel.org/linux-riscv/20190211043829.30096-1-michaeljclark@xxxxxxx/
- Using cmpxchg loop to implement sub-word atomic

Guo Ren (14):
asm-generic: ticket-lock: Reuse arch_spinlock_t of qspinlock
asm-generic: ticket-lock: Add separate ticket-lock.h
riscv: errata: Move errata vendor func-id into vendorid_list.h
riscv: qspinlock: errata: Add ERRATA_THEAD_WRITE_ONCE fixup
riscv: qspinlock: Add basic queued_spinlock support
riscv: qspinlock: Introduce combo spinlock
riscv: qspinlock: Add virt_spin_lock() support for VM guest
riscv: qspinlock: Force virt_spin_lock for KVM guests
RISC-V: paravirt: Add pvqspinlock KVM backend
RISC-V: paravirt: Add pvqspinlock frontend skeleton
RISC-V: paravirt: pvqspinlock: Add SBI implementation
RISC-V: paravirt: pvqspinlock: Add nopvspin kernel parameter
RISC-V: paravirt: pvqspinlock: Add kconfig entry
RISC-V: paravirt: pvqspinlock: Add trace point for pv_kick/wait

.../admin-guide/kernel-parameters.txt | 8 +-
arch/riscv/Kconfig | 35 ++++++
arch/riscv/Kconfig.errata | 19 ++++
arch/riscv/errata/thead/errata.c | 20 ++++
arch/riscv/include/asm/Kbuild | 3 +-
arch/riscv/include/asm/errata_list.h | 18 ---
arch/riscv/include/asm/kvm_vcpu_sbi.h | 1 +
arch/riscv/include/asm/qspinlock.h | 35 ++++++
arch/riscv/include/asm/qspinlock_paravirt.h | 29 +++++
arch/riscv/include/asm/rwonce.h | 31 ++++++
arch/riscv/include/asm/sbi.h | 14 +++
arch/riscv/include/asm/spinlock.h | 88 +++++++++++++++
arch/riscv/include/asm/vendorid_list.h | 19 ++++
arch/riscv/include/uapi/asm/kvm.h | 1 +
arch/riscv/kernel/Makefile | 1 +
arch/riscv/kernel/qspinlock_paravirt.c | 83 ++++++++++++++
arch/riscv/kernel/sbi.c | 2 +-
arch/riscv/kernel/setup.c | 68 ++++++++++++
.../kernel/trace_events_filter_paravirt.h | 60 ++++++++++
arch/riscv/kvm/Makefile | 1 +
arch/riscv/kvm/vcpu_sbi.c | 4 +
arch/riscv/kvm/vcpu_sbi_pvlock.c | 57 ++++++++++
include/asm-generic/qspinlock.h | 2 +
include/asm-generic/rwonce.h | 2 +
include/asm-generic/spinlock.h | 87 +--------------
include/asm-generic/spinlock_types.h | 12 +-
include/asm-generic/ticket_spinlock.h | 105 ++++++++++++++++++
27 files changed, 688 insertions(+), 117 deletions(-)
create mode 100644 arch/riscv/include/asm/qspinlock.h
create mode 100644 arch/riscv/include/asm/qspinlock_paravirt.h
create mode 100644 arch/riscv/include/asm/rwonce.h
create mode 100644 arch/riscv/include/asm/spinlock.h
create mode 100644 arch/riscv/kernel/qspinlock_paravirt.c
create mode 100644 arch/riscv/kernel/trace_events_filter_paravirt.h
create mode 100644 arch/riscv/kvm/vcpu_sbi_pvlock.c
create mode 100644 include/asm-generic/ticket_spinlock.h

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2.40.1