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From: Andrew Murray <andrew.murray@arm.com>
To: Will Deacon <will@kernel.org>
Cc: Mark Rutland <mark.rutland@arm.com>,
	Peter Zijlstra <peterz@infradead.org>,
	Catalin Marinas <catalin.marinas@arm.com>,
	Boqun Feng <boqun.feng@gmail.com>,
	Will Deacon <will.deacon@arm.com>,
	Ard.Biesheuvel@arm.com, linux-arm-kernel@lists.infradead.org
Subject: Re: [PATCH v3 0/5] arm64: avoid out-of-line ll/sc atomics
Date: Wed, 28 Aug 2019 10:04:10 +0100	[thread overview]
Message-ID: <20190828090410.GS14582@e119886-lin.cambridge.arm.com> (raw)
In-Reply-To: <20190827164944.qxk32uas7hx5pjgz@willie-the-truck>

On Tue, Aug 27, 2019 at 05:49:45PM +0100, Will Deacon wrote:
> Hi Andrew,
> 
> On Mon, Aug 12, 2019 at 03:36:20PM +0100, Andrew Murray wrote:
> > When building for LSE atomics (CONFIG_ARM64_LSE_ATOMICS), if the hardware
> > or toolchain doesn't support it the existing code will fallback to ll/sc
> > atomics. It achieves this by branching from inline assembly to a function
> > that is built with specical compile flags. Further this results in the
> > clobbering of registers even when the fallback isn't used increasing
> > register pressure.
> > 
> > Let's improve this by providing inline implementatins of both LSE and
> > ll/sc and use a static key to select between them. This allows for the
> > compiler to generate better atomics code.
> > 
> > Whilst it may be difficult to understand the performance impact, we gain
> > improved code readability, ability to use Clang, and improved backtrace
> > reliability.
> > 
> > Build and boot tested, along with atomic_64_test.
> 
> I think this series is really close now and I was hoping to get something
> queued for 5.4. Would you be able to respin, addressing Mark's comments
> please? It would be a shame for this to miss another release.

Sure, I'm working on this now.

Thanks,

Andrew Murray

> 
> Thanks,
> 
> Will

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      reply	other threads:[~2019-08-28  9:04 UTC|newest]

Thread overview: 18+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-08-12 14:36 [PATCH v3 0/5] arm64: avoid out-of-line ll/sc atomics Andrew Murray
2019-08-12 14:36 ` [PATCH v3 1/5] jump_label: Don't warn on __exit jump entries Andrew Murray
2019-08-22 15:32   ` Mark Rutland
2019-08-22 18:41     ` Andrew Murray
2019-08-12 14:36 ` [PATCH v3 2/5] arm64: Use correct ll/sc atomic constraints Andrew Murray
2019-08-22 15:32   ` Mark Rutland
2019-08-28 13:01     ` Andrew Murray
2019-08-28 15:25       ` Mark Rutland
2019-08-28 15:44         ` Andrew Murray
2019-08-28 16:24           ` Mark Rutland
2019-08-28 16:42             ` Andrew Murray
2019-08-12 14:36 ` [PATCH v3 3/5] arm64: atomics: avoid out-of-line ll/sc atomics Andrew Murray
2019-08-22 17:01   ` Mark Rutland
2019-08-28 11:53     ` Andrew Murray
2019-08-12 14:36 ` [PATCH v3 4/5] arm64: avoid using hard-coded registers for LSE atomics Andrew Murray
2019-08-12 14:36 ` [PATCH v3 5/5] arm64: atomics: remove atomic_ll_sc compilation unit Andrew Murray
2019-08-27 16:49 ` [PATCH v3 0/5] arm64: avoid out-of-line ll/sc atomics Will Deacon
2019-08-28  9:04   ` Andrew Murray [this message]

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