From: Peter Zijlstra <peterz@infradead.org>
To: Ingo Molnar <mingo@kernel.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,
Matthias Kaehlcke <mka@chromium.org>,
Arnd Bergmann <arnd@arndb.de>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
Thomas Gleixner <tglx@linutronix.de>,
Andrew Morton <akpm@linux-foundation.org>,
James Y Knight <jyknight@google.com>,
Chandler Carruth <chandlerc@google.com>,
Stephen Hines <srhines@google.com>,
Nick Desaulniers <ndesaulniers@google.com>,
Kees Cook <keescook@google.com>,
Guenter Roeck <groeck@chromium.org>,
Greg Hackmann <ghackmann@google.com>,
Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Subject: Re: [GIT PULL] x86/build changes for v4.17
Date: Thu, 5 Apr 2018 10:24:09 +0200 [thread overview]
Message-ID: <20180405082409.GK4082@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <20180405080446.qomyc6ozug3g57gl@gmail.com>
On Thu, Apr 05, 2018 at 10:04:46AM +0200, Ingo Molnar wrote:
> http://www.agner.org/optimize/instruction_tables.pdf
>
> The SkyLake costs for 'BT', 'AND' and 'TEST' variants are:
>
> BT m,i 2 2 p06 p23 0.5
> TEST m,r/i 1 2 p0156 p23 1 0.5
These two I would imagine (I tend to forget about the TEST instruction).
And while they're of equal speed, TEST has more ports available if I
read that right. But yes, on SKL it doesn't matter much.
But if you go back in history (a lot) then you'll find BT being far more
expensive than TEST.
On the original Pentium for example TEST-m,r/i is 2 cycles, but BT-m,i
is 4-9 cycles.
But yes, going by the tables that's all hysterical raisins, modern cores
don't much care.
next prev parent reply other threads:[~2018-04-05 8:24 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-04-02 9:50 Ingo Molnar
2018-04-02 21:44 ` Linus Torvalds
2018-04-02 22:38 ` Matthias Kaehlcke
2018-04-03 1:26 ` Matthias Kaehlcke
2018-04-03 8:59 ` Peter Zijlstra
2018-04-03 9:51 ` Ingo Molnar
2018-04-03 12:09 ` Peter Zijlstra
2018-04-03 18:06 ` Matthias Kaehlcke
2018-04-03 21:58 ` Nick Desaulniers
2018-04-04 9:19 ` Peter Zijlstra
2018-04-04 9:38 ` Greg KH
2018-04-04 16:49 ` Nick Desaulniers
2018-04-04 17:13 ` Linus Torvalds
2018-04-04 17:46 ` Nick Desaulniers
2018-04-04 23:10 ` Nick Desaulniers
2018-04-04 16:53 ` Nick Desaulniers
2018-04-04 16:59 ` Greg KH
2018-04-04 19:26 ` James Y Knight
2018-04-04 19:42 ` Linus Torvalds
2018-04-04 22:21 ` James Y Knight
2018-04-04 22:29 ` Linus Torvalds
2018-04-05 7:08 ` Peter Zijlstra
2018-04-05 16:21 ` James Y Knight
2018-04-04 19:32 ` Josh Poimboeuf
2018-06-07 19:23 ` Nick Desaulniers
2018-06-07 20:11 ` Greg KH
2018-04-04 9:30 ` Peter Zijlstra
2018-04-04 19:17 ` Matthias Kaehlcke
2018-04-04 20:33 ` Arnd Bergmann
2018-04-04 20:58 ` Matthias Kaehlcke
2018-04-04 21:11 ` Arnd Bergmann
2018-04-04 21:46 ` Matthias Kaehlcke
2018-04-04 21:59 ` Linus Torvalds
2018-04-04 22:17 ` Matthias Kaehlcke
2018-04-04 22:39 ` Linus Torvalds
2018-04-04 23:31 ` Matthias Kaehlcke
2018-04-05 0:05 ` Linus Torvalds
2018-04-05 0:20 ` Kees Cook
2018-04-05 7:24 ` Peter Zijlstra
2018-04-05 8:04 ` Ingo Molnar
2018-04-05 8:24 ` Peter Zijlstra [this message]
2018-04-05 16:43 ` Linus Torvalds
2018-04-05 7:20 ` Peter Zijlstra
2018-04-05 17:46 ` James Y Knight
2018-04-05 18:06 ` Linus Torvalds
2018-04-05 20:51 ` James Y Knight
2018-04-05 21:13 ` Linus Torvalds
2018-04-05 22:51 ` James Y Knight
2018-04-06 2:02 ` Linus Torvalds
2018-04-05 17:47 ` James Y Knight
2018-04-04 23:04 ` Nick Desaulniers
2018-04-03 17:36 ` Linus Torvalds
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