linux-kernel - Re: [PATCH v2 0/2] riscv: enable lockless lockref implementation

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Message-ID: <ZaVRy4y775bfcEUH@andrea>
Date: Mon, 15 Jan 2024 16:39:55 +0100
From: Andrea Parri <parri.andrea@...il.com>
To: Jisheng Zhang <jszhang@...nel.org>
Cc: Paul Walmsley <paul.walmsley@...ive.com>,
	Palmer Dabbelt <palmer@...belt.com>,
	Albert Ou <aou@...s.berkeley.edu>, linux-riscv@...ts.infradead.org,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH v2 0/2] riscv: enable lockless lockref implementation

On Sat, Dec 02, 2023 at 10:03:21PM +0800, Jisheng Zhang wrote:
> 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 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}

For the series,

Reviewed-by: Andrea Parri <parri.andrea@...il.com>  # code audit, QEMU tests

  Andrea