On Sun, Sep 10, 2023 at 04:28:59AM -0400, guo...@kernel.org wrote:
> From: Guo Ren <guo...@linux.alibaba.com>
>
> The requirements of qspinlock have been documented by commit:
> a8ad07e5240c ("asm-generic: qspinlock: Indicate the use of mixed-size
> atomics").
>
> Although RISC-V ISA gives out a weaker forward guarantee LR/SC, which
> doesn't satisfy the requirements of qspinlock above, it won't prevent
> some riscv vendors from implementing a strong fwd guarantee LR/SC in
> microarchitecture to match xchg_tail requirement. T-HEAD C9xx processor
> is the one.
>
> 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.
>
> Signed-off-by: Guo Ren <guo...@kernel.org>
> Signed-off-by: Guo Ren <guo...@linux.alibaba.com>
> ---
> arch/riscv/Kconfig | 16 ++++++++++++++++
> arch/riscv/include/asm/Kbuild | 3 ++-
> arch/riscv/include/asm/spinlock.h | 17 +++++++++++++++++
> 3 files changed, 35 insertions(+), 1 deletion(-)
> create mode 100644 arch/riscv/include/asm/spinlock.h
>
> diff --git a/arch/riscv/Kconfig b/arch/riscv/Kconfig
> index 2c346fe169c1..7f39bfc75744 100644
> --- a/arch/riscv/Kconfig
> +++ b/arch/riscv/Kconfig
> @@ -471,6 +471,22 @@ config NODES_SHIFT
> Specify the maximum number of NUMA Nodes available on the target
> system. Increases memory reserved to accommodate various tables.
>
> +choice
> + prompt "RISC-V spinlock type"
> + default RISCV_TICKET_SPINLOCKS
> +
> +config RISCV_TICKET_SPINLOCKS
> + bool "Using ticket spinlock"
> +
> +config RISCV_QUEUED_SPINLOCKS
> + bool "Using queued spinlock"
> + depends on SMP && MMU
> + select ARCH_USE_QUEUED_SPINLOCKS
> + help
> + Make sure your micro arch LL/SC has a strong forward progress
> guarantee.
> + Otherwise, stay at ticket-lock.
> +endchoice
> +
> config RISCV_ALTERNATIVE
> bool
> depends on !XIP_KERNEL
> diff --git a/arch/riscv/include/asm/Kbuild b/arch/riscv/include/asm/Kbuild
> index 504f8b7e72d4..a0dc85e4a754 100644
> --- a/arch/riscv/include/asm/Kbuild
> +++ b/arch/riscv/include/asm/Kbuild
> @@ -2,10 +2,11 @@
> generic-y += early_ioremap.h
> generic-y += flat.h
> generic-y += kvm_para.h
> +generic-y += mcs_spinlock.h
> generic-y += parport.h
> -generic-y += spinlock.h
IIUC here you take the asm-generic/spinlock.h (which defines arch_spin_*())
and include the asm-generic headers of mcs_spinlock and qspinlock.
In this case, the qspinlock.h will provide the arch_spin_*() interfaces,
which seems the oposite of the above description (ticket spinlocks being
the standard).
Shouldn't ticket-spinlock.h also get included here?
(Also, I am probably missing something, as I dont' see the use of
mcs_spinlock here.)
> generic-y += spinlock_types.h
> generic-y += qrwlock.h
> generic-y += qrwlock_types.h
> +generic-y += qspinlock.h
> generic-y += user.h
> generic-y += vmlinux.lds.h
> diff --git a/arch/riscv/include/asm/spinlock.h
> b/arch/riscv/include/asm/spinlock.h
> new file mode 100644
> index 000000000000..c644a92d4548
> --- /dev/null
> +++ b/arch/riscv/include/asm/spinlock.h
> @@ -0,0 +1,17 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +
> +#ifndef __ASM_RISCV_SPINLOCK_H
> +#define __ASM_RISCV_SPINLOCK_H
> +
> +#ifdef CONFIG_QUEUED_SPINLOCKS
> +#define _Q_PENDING_LOOPS (1 << 9)
> +#endif
Any reason the above define couldn't be merged on the ifdef below?
> +
> +#ifdef CONFIG_QUEUED_SPINLOCKS
> +#include <asm/qspinlock.h>
> +#include <asm/qrwlock.h>
> +#else
> +#include <asm-generic/spinlock.h>
> +#endif
> +
> +#endif /* __ASM_RISCV_SPINLOCK_H */
> --
> 2.36.1
>
Thanks!
Leo
