On Fri, Sep 15, 2023 at 5:08 PM Leonardo Bras <leobras@xxxxxxxxxx> wrote:
>
> On Fri, Sep 15, 2023 at 10:10:25AM +0800, Guo Ren wrote:
> > On Thu, Sep 14, 2023 at 5:43 PM Leonardo Bras <leobras@xxxxxxxxxx> wrote:
> > >
> > > On Thu, Sep 14, 2023 at 12:46:56PM +0800, Guo Ren wrote:
> > > > On Thu, Sep 14, 2023 at 4:29 AM Leonardo Bras <leobras@xxxxxxxxxx> wrote:
> > > > >
> > > > > On Sun, Sep 10, 2023 at 04:28:59AM -0400, guoren@xxxxxxxxxx wrote:
> > > > > > From: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
> > > > > >
> > > > > > 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 <guoren@xxxxxxxxxx>
> > > > > > Signed-off-by: Guo Ren <guoren@xxxxxxxxxxxxxxxxx>
> > > > > > ---
> > > > > > 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.)
> > > > No, because asm-generic/spinlock.h:
> > > > ...
> > > > #include <asm-generic/ticket_spinlock.h>
> > > > ...
> > > >
> > >
> > > But aren't you removing asm-generic/spinlock.h below ?
> > > -generic-y += spinlock.h
> > Yes, current is:
> >
> > arch/riscv/include/asm/spinlock.h -> include/asm-generic/spinlock.h ->
> > include/asm-generic/ticket_spinlock.h
>
> I did a little reading on how generic-y works (which I was unaware):
>
> "If an architecture uses a verbatim copy of a header from
> include/asm-generic then this is listed in the file
> arch/$(SRCARCH)/include/asm/Kbuild [...] During the prepare phase of the
> build a wrapper include file is generated in the directory [...]"
>
> Oh, so you are removing the asm-generic/spinlock.h because it's link
> was replaced by a new asm/spinlock.h.
>
> You add qspinlock.h to generic-y because it's new in riscv, and add
> mcs_spinlock.h because it's needed by qspinlock.h.
>
> Ok, it makes sense now.
>
> Sorry about this noise.
> I was unaware of how generic-y worked, and (wrongly)
> assumed it was about including headers automatically in the build.
>
>
> >
> > +#ifdef CONFIG_QUEUED_SPINLOCKS
> > +#include <asm/qspinlock.h>
> > +#include <asm/qrwlock.h>
> > +#else
> > +#include <asm-generic/spinlock.h>
> > +#endif
> >
> > So, you want me:
> > +#ifdef CONFIG_QUEUED_SPINLOCKS
> > +#include <asm/qspinlock.h>
> > +#else
> > +#include <asm-generic/ticket_spinlock.h>
> > +#endif
> >
> > +#include <asm/qrwlock.h>
> >
> > Right?
>
> No, I didn't mean that.
> I was just worried about the arch_spin_*() interfaces, but they should be
> fine.
>
> BTW, according to kernel doc on generic-y, shouldn't be a better idea to
> add 'ticket_spinlock.h' to generic-y, and include above as
> asm/ticket_spinlock.h?
>
> Or is generic-y reserved only for stuff which is indirectly included by
> other headers?
It's okay to add generic-y for ticket_spinlock.h, and I'm okay with
the following:
+#ifdef CONFIG_QUEUED_SPINLOCKS
+#include <asm/qspinlock.h>
+#else
+#include <asm/ticket_spinlock.h>
+#endif
+#include <asm/qrwlock.h>
>
> Thanks!
> Leo
>
> >
> > >
> > > > >
> > > > > > 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?
> > > > Easy for the next patch to modify. See Waiman's comment:
> > > >
> > > > https://lore.kernel.org/linux-riscv/4cc7113a-0e4e-763a-cba2-7963bcd26c7a@xxxxxxxxxx/
> > > >
> > > > > diff --git a/arch/riscv/include/asm/spinlock.h b/arch/riscv/include/asm/spinlock.h
> > > > > index c644a92d4548..9eb3ad31e564 100644
> > > > > --- a/arch/riscv/include/asm/spinlock.h
> > > > > +++ b/arch/riscv/include/asm/spinlock.h
> > > > > @@ -7,11 +7,94 @@
> > > > > #define _Q_PENDING_LOOPS (1 << 9)
> > > > > #endif
> > > > >
> > > >
> > > > I see why you separated the _Q_PENDING_LOOPS out.
> > > >
> > >
> > > I see, should be fine then.
> > >
> > > Thanks!
> > > Leo
> > >
> > > >
> > > > >
> > > > > > +
> > > > > > +#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
> > > > >
> > > >
> > > >
> > > > --
> > > > Best Regards
> > > > Guo Ren
> > > >
> > >
> >
> >
> > --
> > Best Regards
> > Guo Ren
> >
>
--
Best Regards
Guo Ren
