linux-kernel - [PATCH v3 0/2] riscv: enable lockless lockref implementation

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Message-ID: <20240125145908.968-1-jszhang@kernel.org>
Date: Thu, 25 Jan 2024 22:59:05 +0800
From: Jisheng Zhang <jszhang@...nel.org>
To: Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>
Cc: linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: [PATCH v3 0/2] riscv: enable lockless lockref implementation

This series selects ARCH_USE_CMPXCHG_LOCKREF to enable the
cmpxchg-based lockless lockref implementation for riscv. Then,
implement arch_cmpxchg64_{relaxed|acquire|release}.

After patch1:
Using Linus' test case[1] on TH1520 platform, I see a 11.2% improvement.
On JH7110 platform, I see 12.0% improvement.

After patch2:
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]

Since v2:
  - rebase on v6.8-rc1
  - collect Reviewed-by tag

Since v1:
  - only select ARCH_USE_CMPXCHG_LOCKREF if 64BIT

Jisheng Zhang (2):
  riscv: select ARCH_USE_CMPXCHG_LOCKREF
  riscv: cmpxchg: implement arch_cmpxchg64_{relaxed|acquire|release}

 arch/riscv/Kconfig               |  1 +
 arch/riscv/include/asm/cmpxchg.h | 18 ++++++++++++++++++
 2 files changed, 19 insertions(+)

-- 
2.43.0