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From: Richard Henderson <rth@twiddle.net>
To: "Emilio G. Cota" <cota@braap.org>,
	QEMU Developers <qemu-devel@nongnu.org>,
	MTTCG Devel <mttcg@greensocs.com>
Cc: "Alex Bennée" <alex.bennee@linaro.org>,
	"Paolo Bonzini" <pbonzini@redhat.com>,
	"Peter Crosthwaite" <crosthwaite.peter@gmail.com>,
	"Peter Maydell" <peter.maydell@linaro.org>,
	"Sergey Fedorov" <serge.fdrv@gmail.com>
Subject: Re: [Qemu-devel] [PATCH v2 05/13] include/processor.h: define cpu_relax()
Date: Fri, 8 Apr 2016 11:33:17 -0700	[thread overview]
Message-ID: <5707F96D.8040705@twiddle.net> (raw)
In-Reply-To: <1460050358-25025-6-git-send-email-cota@braap.org>

On 04/07/2016 10:32 AM, Emilio G. Cota wrote:
> Taken from the linux kernel.
> 
> Signed-off-by: Emilio G. Cota <cota@braap.org>
> ---
>  include/qemu/processor.h | 28 ++++++++++++++++++++++++++++
>  1 file changed, 28 insertions(+)
>  create mode 100644 include/qemu/processor.h

Reviewed-by: Richard Henderson  <rth@twiddle.net>


> +#if defined(__i386__) || defined(__x86_64__)
> +#define cpu_relax() asm volatile("rep; nop" ::: "memory")
> +#endif

Not that it matters much, but for the record there's an ICC inspired builtin in
<xmmintrin.h> for this: _mm_pause().  But so long as we're always using gcc or
clang, that's probably just an extra dependency to worry about.


r~

  reply	other threads:[~2016-04-08 18:33 UTC|newest]

Thread overview: 28+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2016-04-07 17:32 [Qemu-devel] [PATCH v2 00/10] tb hash improvements Emilio G. Cota
2016-04-07 17:32 ` [Qemu-devel] [PATCH v2 02/13] compiler.h: add QEMU_ALIGNED() to enforce struct alignment Emilio G. Cota
2016-04-08 18:26   ` Richard Henderson
2016-04-07 17:32 ` [Qemu-devel] [PATCH v2 03/13] seqlock: remove optional mutex Emilio G. Cota
2016-04-08 18:26   ` Richard Henderson
2016-04-07 17:32 ` [Qemu-devel] [PATCH v2 04/13] seqlock: rename write_lock/unlock to write_begin/end Emilio G. Cota
2016-04-08 18:27   ` Richard Henderson
2016-04-07 17:32 ` [Qemu-devel] [PATCH v2 05/13] include/processor.h: define cpu_relax() Emilio G. Cota
2016-04-08 18:33   ` Richard Henderson [this message]
2016-04-07 17:32 ` [Qemu-devel] [PATCH v2 06/13] qemu-thread: add simple test-and-set spinlock Emilio G. Cota
2016-04-08 13:02   ` Alex Bennée
2016-04-08 18:38     ` Richard Henderson
2016-04-08 21:24       ` Alex Bennée
2016-04-08 21:26         ` Paolo Bonzini
2016-04-08 21:31           ` Richard Henderson
2016-04-08 21:35             ` Sergey Fedorov
2016-04-08 18:35   ` Richard Henderson
2016-04-07 17:32 ` [Qemu-devel] [PATCH v2 07/13] qemu-thread: call cpu_relax() while spinning Emilio G. Cota
2016-04-08 18:39   ` Richard Henderson
2016-04-07 17:32 ` [Qemu-devel] [PATCH v2 08/13] qemu-thread: optimize spin_lock for uncontended locks Emilio G. Cota
2016-04-08 18:40   ` Richard Henderson
2016-04-07 17:32 ` [Qemu-devel] [PATCH v2 09/13] exec: add tb_hash_func5, derived from xxhash Emilio G. Cota
2016-04-08 18:45   ` Richard Henderson
2016-04-07 17:32 ` [Qemu-devel] [PATCH v2 10/13] tb hash: hash phys_pc, pc, and flags with xxhash Emilio G. Cota
2016-04-08 18:48   ` Richard Henderson
2016-04-07 17:32 ` [Qemu-devel] [PATCH v2 12/13] qht: add test program Emilio G. Cota
2016-04-08 12:41 ` [Qemu-devel] [PATCH v2 00/10] tb hash improvements Alex Bennée
     [not found] ` <1460050358-25025-2-git-send-email-cota@braap.org>
2016-04-08 18:25   ` [Qemu-devel] [PATCH v2 01/13] translate-all: add missing fold of tb_ctx into tcg_ctx Richard Henderson

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