From: "H. Peter Anvin" <hpa@zytor.com>
To: Steven Rostedt <rostedt@goodmis.org>
Cc: Masami Hiramatsu <masami.hiramatsu.pt@hitachi.com>,
linux-kernel@vger.kernel.org, Ingo Molnar <mingo@elte.hu>,
Andrew Morton <akpm@linux-foundation.org>,
Thomas Gleixner <tglx@linutronix.de>,
Frederic Weisbecker <fweisbec@gmail.com>,
yrl.pp-manager.tt@hitachi.com
Subject: Re: [RFC][PATCH 2/4 v4] ftrace/x86: Add save_regs for i386 function calls
Date: Thu, 19 Jul 2012 15:53:08 -0700 [thread overview]
Message-ID: <50088FD4.4060401@zytor.com> (raw)
In-Reply-To: <1342702682.12353.20.camel@gandalf.stny.rr.com>
On 07/19/2012 05:58 AM, Steven Rostedt wrote:
>>
>> also, because lea is faster than add (and doesn't even modify flags), I
>> changed the last part to use lea instead of addl.
>
> Now I'm told that this is not always the case (at least not for Atom),
> so I reverted this part and put back the addl. But can you still give
> you reviewed by for the first part?
>
lea is not typically faster than add, but in the case of Atom, it is
done in an earlier pipeline stage (AGU instead of ALU) which means lea
is faster if its inputs are already available as address expressions and
is consumed by address expressions; the goal is to avoid the ALU->AGU
forwarding latency.
-hpa
next prev parent reply other threads:[~2012-07-19 22:53 UTC|newest]
Thread overview: 23+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-07-11 19:50 [RFC][PATCH 0/4 v4] ftrace/kprobes: Setting up ftrace for kprobes Steven Rostedt
2012-07-11 19:50 ` [RFC][PATCH 1/4 v4] ftrace/x86: Add separate function to save regs Steven Rostedt
2012-07-12 12:12 ` Masami Hiramatsu
2012-07-11 19:50 ` [RFC][PATCH 2/4 v4] ftrace/x86: Add save_regs for i386 function calls Steven Rostedt
2012-07-12 12:39 ` Masami Hiramatsu
2012-07-12 15:53 ` Steven Rostedt
2012-07-13 18:47 ` Steven Rostedt
2012-07-17 2:08 ` Masami Hiramatsu
2012-07-17 3:05 ` Steven Rostedt
2012-07-17 3:13 ` Masami Hiramatsu
2012-07-18 15:59 ` Steven Rostedt
2012-07-19 2:20 ` Masami Hiramatsu
2012-07-19 12:52 ` Steven Rostedt
2012-07-19 12:58 ` Steven Rostedt
2012-07-19 22:53 ` H. Peter Anvin [this message]
2012-07-19 23:04 ` Steven Rostedt
2012-07-19 23:07 ` H. Peter Anvin
2012-07-20 1:27 ` Steven Rostedt
2012-07-19 18:24 ` Steven Rostedt
2012-08-21 15:03 ` [tip:perf/core] ftrace/x86_32: Simplify parameter setup for ftrace_regs_caller tip-bot for Uros Bizjak
2012-07-11 19:50 ` [RFC][PATCH 3/4 v4] ftrace/x86: Remove function_trace_stop check from graph caller Steven Rostedt
2012-08-21 15:04 ` [tip:perf/core] " tip-bot for Steven Rostedt
2012-07-11 19:50 ` [RFC][PATCH 4/4 v4] ftrace/x86_64: Add recursion protection inside mcount caller Steven Rostedt
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