From: Borislav Petkov <bp@alien8.de>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Ingo Molnar <mingo@kernel.org>,
Wedson Almeida Filho <wedsonaf@gmail.com>,
Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
x86@kernel.org, linux-kernel@vger.kernel.org,
Linus Torvalds <torvalds@linux-foundation.org>,
Andrew Morton <akpm@linux-foundation.org>,
Peter Zijlstra <a.p.zijlstra@chello.nl>
Subject: Re: [PATCH] x86: Use asm-goto to implement mutex fast path on x86-64
Date: Mon, 1 Jul 2013 16:36:47 +0200 [thread overview]
Message-ID: <20130701143646.GG23515@pd.tnic> (raw)
In-Reply-To: <19b76ce4-35e0-4f82-b7e9-aa07d5d8af2c@email.android.com>
On Mon, Jul 01, 2013 at 07:30:14AM -0700, H. Peter Anvin wrote:
> Unconditional branches don't need prediction. The branch predictor
> is used for conditional branches and in some hardware designs for
> indirect branches. Unconditional direct branches never go through
> the branch predictor simply because the front end can know with 100%
> certainty where the flow of control will be.
I meant the conditional Jcc branches:
ffffffff81774920 <mutex_lock>:
...
ffffffff8177492d: f0 ff 0b lock decl (%rbx)
ffffffff81774930: 79 08 jns ffffffff8177493a <mutex_lock+0x1a>
ffffffff81774730 <mutex_unlock>:
...
ffffffff81774738: f0 ff 07 lock incl (%rdi)
ffffffff8177473b: 7f 0a jg ffffffff81774747 <mutex_unlock+0x17>
--
Regards/Gruss,
Boris.
Sent from a fat crate under my desk. Formatting is fine.
--
next prev parent reply other threads:[~2013-07-01 14:36 UTC|newest]
Thread overview: 24+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-06-28 10:54 [PATCH] x86: Use asm-goto to implement mutex fast path on x86-64 Wedson Almeida Filho
2013-06-28 11:19 ` Ingo Molnar
2013-06-28 14:09 ` Borislav Petkov
2013-06-28 14:12 ` H. Peter Anvin
2013-06-28 15:15 ` Peter Zijlstra
2013-06-28 16:41 ` [PATCH] x86, cpufeature: Use new CC_HAVE_ASM_GOTO Borislav Petkov
2013-07-05 14:24 ` [tip:x86/cpu] " tip-bot for Borislav Petkov
2013-06-29 23:56 ` [PATCH] x86: Use asm-goto to implement mutex fast path on x86-64 Wedson Almeida Filho
2013-06-30 22:00 ` Borislav Petkov
2013-07-01 7:50 ` Ingo Molnar
2013-07-01 10:23 ` Borislav Petkov
2013-07-01 11:11 ` Ingo Molnar
2013-07-01 12:29 ` Borislav Petkov
2013-07-01 12:50 ` Ingo Molnar
2013-07-01 14:48 ` Borislav Petkov
2013-07-01 22:28 ` Borislav Petkov
2013-07-01 22:35 ` Wedson Almeida Filho
2013-07-01 22:44 ` Borislav Petkov
2013-07-02 6:39 ` Ingo Molnar
2013-07-02 10:29 ` Borislav Petkov
2013-07-01 14:30 ` H. Peter Anvin
2013-07-01 14:36 ` Borislav Petkov [this message]
2013-07-01 14:45 ` H. Peter Anvin
2013-07-01 14:50 ` Borislav Petkov
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