From: will.deacon@arm.com (Will Deacon)
To: linux-arm-kernel@lists.infradead.org
Subject: [RFC PATCH] arm64: Implement cpu_relax as yield
Date: Wed, 25 Feb 2015 13:24:38 +0000 [thread overview]
Message-ID: <20150225132437.GD12377@arm.com> (raw)
In-Reply-To: <1424819257-22664-1-git-send-email-peter.crosthwaite@xilinx.com>
On Tue, Feb 24, 2015 at 11:07:37PM +0000, Peter Crosthwaite wrote:
> ARM64 has the yield nop hint which has the intended semantics of
> cpu_relax. Implement.
>
> The immediate application is ARM CPU emulators. An emulator can take
> advantage of the yield hint to de-prioritise an emulated CPU in favor
> of other emulation tasks. QEMU A64 SMP emulation has yield awareness,
> and sees a significant boot time performance increase with this change.
Could you elaborate on the QEMU SMP boot case please? Usually SMP pens
for booting make use of wfe/sev to minimise the spinning overhead.
Will
WARNING: multiple messages have this Message-ID (diff)
From: Will Deacon <will.deacon@arm.com>
To: Peter Crosthwaite <peter.crosthwaite@xilinx.com>
Cc: "linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Catalin Marinas <Catalin.Marinas@arm.com>,
"michals@xilinx.com" <michals@xilinx.com>
Subject: Re: [RFC PATCH] arm64: Implement cpu_relax as yield
Date: Wed, 25 Feb 2015 13:24:38 +0000 [thread overview]
Message-ID: <20150225132437.GD12377@arm.com> (raw)
In-Reply-To: <1424819257-22664-1-git-send-email-peter.crosthwaite@xilinx.com>
On Tue, Feb 24, 2015 at 11:07:37PM +0000, Peter Crosthwaite wrote:
> ARM64 has the yield nop hint which has the intended semantics of
> cpu_relax. Implement.
>
> The immediate application is ARM CPU emulators. An emulator can take
> advantage of the yield hint to de-prioritise an emulated CPU in favor
> of other emulation tasks. QEMU A64 SMP emulation has yield awareness,
> and sees a significant boot time performance increase with this change.
Could you elaborate on the QEMU SMP boot case please? Usually SMP pens
for booting make use of wfe/sev to minimise the spinning overhead.
Will
next prev parent reply other threads:[~2015-02-25 13:24 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-02-24 23:07 [RFC PATCH] arm64: Implement cpu_relax as yield Peter Crosthwaite
2015-02-24 23:07 ` Peter Crosthwaite
2015-02-25 13:24 ` Will Deacon [this message]
2015-02-25 13:24 ` Will Deacon
2015-02-27 19:43 ` Peter Crosthwaite
2015-02-27 19:43 ` Peter Crosthwaite
2015-02-27 19:53 ` Will Deacon
2015-02-27 19:53 ` Will Deacon
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