From: Jisheng Zhang <jszhang@kernel.org> To: Paul Walmsley <paul.walmsley@sifive.com>, Palmer Dabbelt <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu> Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Andrea Parri <parri.andrea@gmail.com> Subject: [PATCH v3 2/2] riscv: cmpxchg: implement arch_cmpxchg64_{relaxed|acquire|release} Date: Thu, 25 Jan 2024 22:59:07 +0800 [thread overview] Message-ID: <20240125145908.968-3-jszhang@kernel.org> (raw) In-Reply-To: <20240125145908.968-1-jszhang@kernel.org> After selecting ARCH_USE_CMPXCHG_LOCKREF, one straight futher optimization is implementing the arch_cmpxchg64_relaxed() because the lockref code does not need the cmpxchg to have barrier semantics. At the same time, implement arch_cmpxchg64_acquire and arch_cmpxchg64_release as well. However, on both TH1520 and JH7110 platforms, I didn't see obvious performance improvement with Linus' test case [1]. IMHO, this may be related with the fence and lr.d/sc.d hw implementations. In theory, lr/sc without fence could give performance improvement over lr/sc plus fence, so add the code here to leave performance improvement room on newer HW platforms. Link: http://marc.info/?l=linux-fsdevel&m=137782380714721&w=4 [1] Signed-off-by: Jisheng Zhang <jszhang@kernel.org> Reviewed-by: Andrea Parri <parri.andrea@gmail.com> --- arch/riscv/include/asm/cmpxchg.h | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/arch/riscv/include/asm/cmpxchg.h b/arch/riscv/include/asm/cmpxchg.h index 2f4726d3cfcc..6318187f426f 100644 --- a/arch/riscv/include/asm/cmpxchg.h +++ b/arch/riscv/include/asm/cmpxchg.h @@ -360,4 +360,22 @@ arch_cmpxchg_relaxed((ptr), (o), (n)); \ }) +#define arch_cmpxchg64_relaxed(ptr, o, n) \ +({ \ + BUILD_BUG_ON(sizeof(*(ptr)) != 8); \ + arch_cmpxchg_relaxed((ptr), (o), (n)); \ +}) + +#define arch_cmpxchg64_acquire(ptr, o, n) \ +({ \ + BUILD_BUG_ON(sizeof(*(ptr)) != 8); \ + arch_cmpxchg_acquire((ptr), (o), (n)); \ +}) + +#define arch_cmpxchg64_release(ptr, o, n) \ +({ \ + BUILD_BUG_ON(sizeof(*(ptr)) != 8); \ + arch_cmpxchg_release((ptr), (o), (n)); \ +}) + #endif /* _ASM_RISCV_CMPXCHG_H */ -- 2.43.0
WARNING: multiple messages have this Message-ID (diff)
From: Jisheng Zhang <jszhang@kernel.org> To: Paul Walmsley <paul.walmsley@sifive.com>, Palmer Dabbelt <palmer@dabbelt.com>, Albert Ou <aou@eecs.berkeley.edu> Cc: linux-riscv@lists.infradead.org, linux-kernel@vger.kernel.org, Andrea Parri <parri.andrea@gmail.com> Subject: [PATCH v3 2/2] riscv: cmpxchg: implement arch_cmpxchg64_{relaxed|acquire|release} Date: Thu, 25 Jan 2024 22:59:07 +0800 [thread overview] Message-ID: <20240125145908.968-3-jszhang@kernel.org> (raw) In-Reply-To: <20240125145908.968-1-jszhang@kernel.org> After selecting ARCH_USE_CMPXCHG_LOCKREF, one straight futher optimization is implementing the arch_cmpxchg64_relaxed() because the lockref code does not need the cmpxchg to have barrier semantics. At the same time, implement arch_cmpxchg64_acquire and arch_cmpxchg64_release as well. However, on both TH1520 and JH7110 platforms, I didn't see obvious performance improvement with Linus' test case [1]. IMHO, this may be related with the fence and lr.d/sc.d hw implementations. In theory, lr/sc without fence could give performance improvement over lr/sc plus fence, so add the code here to leave performance improvement room on newer HW platforms. Link: http://marc.info/?l=linux-fsdevel&m=137782380714721&w=4 [1] Signed-off-by: Jisheng Zhang <jszhang@kernel.org> Reviewed-by: Andrea Parri <parri.andrea@gmail.com> --- arch/riscv/include/asm/cmpxchg.h | 18 ++++++++++++++++++ 1 file changed, 18 insertions(+) diff --git a/arch/riscv/include/asm/cmpxchg.h b/arch/riscv/include/asm/cmpxchg.h index 2f4726d3cfcc..6318187f426f 100644 --- a/arch/riscv/include/asm/cmpxchg.h +++ b/arch/riscv/include/asm/cmpxchg.h @@ -360,4 +360,22 @@ arch_cmpxchg_relaxed((ptr), (o), (n)); \ }) +#define arch_cmpxchg64_relaxed(ptr, o, n) \ +({ \ + BUILD_BUG_ON(sizeof(*(ptr)) != 8); \ + arch_cmpxchg_relaxed((ptr), (o), (n)); \ +}) + +#define arch_cmpxchg64_acquire(ptr, o, n) \ +({ \ + BUILD_BUG_ON(sizeof(*(ptr)) != 8); \ + arch_cmpxchg_acquire((ptr), (o), (n)); \ +}) + +#define arch_cmpxchg64_release(ptr, o, n) \ +({ \ + BUILD_BUG_ON(sizeof(*(ptr)) != 8); \ + arch_cmpxchg_release((ptr), (o), (n)); \ +}) + #endif /* _ASM_RISCV_CMPXCHG_H */ -- 2.43.0 _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv
next prev parent reply other threads:[~2024-01-25 15:12 UTC|newest] Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top 2024-01-25 14:59 [PATCH v3 0/2] riscv: enable lockless lockref implementation Jisheng Zhang 2024-01-25 14:59 ` Jisheng Zhang 2024-01-25 14:59 ` [PATCH v3 1/2] riscv: select ARCH_USE_CMPXCHG_LOCKREF Jisheng Zhang 2024-01-25 14:59 ` Jisheng Zhang 2024-01-25 14:59 ` Jisheng Zhang [this message] 2024-01-25 14:59 ` [PATCH v3 2/2] riscv: cmpxchg: implement arch_cmpxchg64_{relaxed|acquire|release} Jisheng Zhang
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