From: Guo Ren <guoren@kernel.org>
To: Andrew Jones <ajones@ventanamicro.com>
Cc: wefu@redhat.com, keescook@chromium.org, peterz@infradead.org,
unicorn_wang@outlook.com, atishp@atishpatra.org,
chao.wei@sophgo.com, bjorn@rivosinc.com,
linux-kernel@vger.kernel.org, xiaoguang.xing@sophgo.com,
conor.dooley@microchip.com, leobras@redhat.com,
palmer@dabbelt.com, jszhang@kernel.org, paul.walmsley@sifive.com,
Guo Ren <guoren@linux.alibaba.com>,
panqinglin2020@iscas.ac.cn, linux-riscv@lists.infradead.org,
wuwei2016@iscas.ac.cn
Subject: Re: [PATCH V2 3/3] riscv: xchg: Prefetch the destination word for sc.w
Date: Wed, 3 Jan 2024 14:15:45 +0800 [thread overview]
Message-ID: <CAJF2gTQ7Oo8UKdPRs0GAAUsh9mDCgGucS8g8kuPzByaWVOtigw@mail.gmail.com> (raw)
In-Reply-To: <20240102-81391283df04c430d76c0eb0@orel>
On Tue, Jan 2, 2024 at 7:19 PM Andrew Jones <ajones@ventanamicro.com> wrote:
>
> On Sun, Dec 31, 2023 at 03:29:53AM -0500, guoren@kernel.org wrote:
> > From: Guo Ren <guoren@linux.alibaba.com>
> >
> > The cost of changing a cacheline from shared to exclusive state can be
> > significant, especially when this is triggered by an exclusive store,
> > since it may result in having to retry the transaction.
> >
> > This patch makes use of prefetch.w to prefetch cachelines for write
> > prior to lr/sc loops when using the xchg_small atomic routine.
> >
> > This patch is inspired by commit: 0ea366f5e1b6 ("arm64: atomics:
> > prefetch the destination word for write prior to stxr").
> >
> > Signed-off-by: Guo Ren <guoren@linux.alibaba.com>
> > Signed-off-by: Guo Ren <guoren@kernel.org>
> > ---
> > arch/riscv/include/asm/cmpxchg.h | 4 +++-
> > 1 file changed, 3 insertions(+), 1 deletion(-)
> >
> > diff --git a/arch/riscv/include/asm/cmpxchg.h b/arch/riscv/include/asm/cmpxchg.h
> > index 26cea2395aae..d7b9d7951f08 100644
> > --- a/arch/riscv/include/asm/cmpxchg.h
> > +++ b/arch/riscv/include/asm/cmpxchg.h
> > @@ -10,6 +10,7 @@
> >
> > #include <asm/barrier.h>
> > #include <asm/fence.h>
> > +#include <asm/processor.h>
> >
> > #define __arch_xchg_masked(prepend, append, r, p, n) \
>
> Are you sure this is based on v6.7-rc7? Because I don't see this macro.
Oh, it is based on Leobras' patches. I would remove it in the next of version.
>
> > ({ \
> > @@ -23,6 +24,7 @@
> > \
> > __asm__ __volatile__ ( \
> > prepend \
> > + PREFETCHW_ASM(%5) \
> > "0: lr.w %0, %2\n" \
> > " and %1, %0, %z4\n" \
> > " or %1, %1, %z3\n" \
> > @@ -30,7 +32,7 @@
> > " bnez %1, 0b\n" \
> > append \
> > : "=&r" (__retx), "=&r" (__rc), "+A" (*(__ptr32b)) \
> > - : "rJ" (__newx), "rJ" (~__mask) \
> > + : "rJ" (__newx), "rJ" (~__mask), "rJ" (__ptr32b) \
>
> I'm pretty sure we don't want to allow the J constraint for __ptr32b.
>
> > : "memory"); \
> > \
> > r = (__typeof__(*(p)))((__retx & __mask) >> __s); \
> > --
> > 2.40.1
> >
>
> Thanks,
> drew
--
Best Regards
Guo Ren
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next prev parent reply other threads:[~2024-01-03 6:16 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-12-31 8:29 [PATCH V2 0/3] riscv: Add Zicbop & prefetchw support guoren
2023-12-31 8:29 ` [PATCH V2 1/3] riscv: Add Zicbop instruction definitions & cpufeature guoren
2024-01-02 10:32 ` Andrew Jones
2024-01-03 6:13 ` Guo Ren
2024-01-03 6:49 ` Andrew Jones
2024-01-03 19:44 ` Andrew Jones
2024-01-03 19:06 ` Leonardo Bras
2024-01-03 9:31 ` Clément Léger
2024-01-03 12:00 ` Andrew Jones
2024-01-11 10:31 ` Clément Léger
2024-01-11 10:45 ` Andrew Jones
2024-01-11 10:49 ` Clément Léger
2024-01-11 11:12 ` Conor Dooley
2024-01-03 18:52 ` Leonardo Bras
2024-01-03 19:29 ` Andrew Jones
2024-01-03 20:33 ` Leonardo Bras
2024-01-04 9:47 ` Andrew Jones
2024-01-04 15:03 ` Leonardo Bras
2024-01-04 16:40 ` Andrew Jones
2024-01-04 17:43 ` Leonardo Bras
2024-01-05 13:24 ` Andrew Jones
2024-01-08 14:34 ` Leonardo Bras
2024-01-08 15:24 ` Andrew Jones
2024-01-08 16:14 ` Leonardo Bras
2024-01-03 19:48 ` Andrew Jones
2024-01-03 20:34 ` Leonardo Bras
2023-12-31 8:29 ` [PATCH V2 2/3] riscv: Add ARCH_HAS_PRETCHW support with Zibop guoren
2024-01-01 2:29 ` Guo Ren
2024-01-03 19:04 ` Leonardo Bras
2024-01-02 10:45 ` Andrew Jones
2024-01-03 6:19 ` Guo Ren
2024-01-03 19:56 ` Andrew Jones
2024-01-05 13:31 ` Andrew Jones
2023-12-31 8:29 ` [PATCH V2 3/3] riscv: xchg: Prefetch the destination word for sc.w guoren
2024-01-02 11:18 ` Andrew Jones
2024-01-03 6:15 ` Guo Ren [this message]
2024-01-03 19:45 ` Leonardo Bras
2024-01-04 1:24 ` Guo Ren
2024-01-04 3:56 ` Leonardo Bras
2024-01-04 8:14 ` Guo Ren
2024-01-04 14:17 ` Leonardo Bras
2024-01-05 1:13 ` Guo Ren
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