From: "H. Peter Anvin" <hpa@zytor.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Arjan van de Ven <arjan@linux.intel.com>,
Ingo Molnar <mingo@kernel.org>,
Peter Zijlstra <peterz@infradead.org>,
Andi Kleen <ak@linux.intel.com>,
Mike Galbraith <bitbucket@online.de>,
Thomas Gleixner <tglx@linutronix.de>,
Frederic Weisbecker <fweisbec@gmail.com>,
Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>
Subject: Re: [PATCH 0/7] preempt_count rework -v2
Date: Wed, 11 Sep 2013 09:00:30 -0700 [thread overview]
Message-ID: <5230939E.3050408@zytor.com> (raw)
In-Reply-To: <CA+55aFz3S6_g4TQ11VKGM3GW=a=r3qYWQ_a0qJ_5241qQz8D=w@mail.gmail.com>
On 09/10/2013 09:24 AM, Linus Torvalds wrote:
> On Tue, Sep 10, 2013 at 8:29 AM, Arjan van de Ven <arjan@linux.intel.com> wrote:
>>>
>> also.. yuck on using "dec"
>> "dec" sucks, please use "sub foo ,1" instead
>
> That's a bigger instruction, largely due to the constant.
>
>> (dec sucks because of its broken flags behavior; it creates basically a
>> bubble in the pipeline)
>
> Intel could (and should) just fix that. It's "easy" enough - you just
> need to rename the carry flag as a separate register (and make sure
> that the conditional instructions that don't use it don't think they
> need it).
>
> In fact I thought Intel already did that on their large cores. Are you
> sure they still have trouble with inc/dec?
>
Big cores are fine, but Atom (and presumably Quark) might still suffer a
performance penalty.
-hpa
next prev parent reply other threads:[~2013-09-11 16:01 UTC|newest]
Thread overview: 52+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-09-10 13:08 [PATCH 0/7] preempt_count rework -v2 Peter Zijlstra
2013-09-10 13:08 ` [PATCH 1/7] sched: Introduce preempt_count accessor functions Peter Zijlstra
2013-09-10 13:08 ` [PATCH 2/7] sched: Add NEED_RESCHED to the preempt_count Peter Zijlstra
2013-09-11 1:59 ` Andy Lutomirski
2013-09-11 8:25 ` Peter Zijlstra
2013-09-11 11:06 ` Peter Zijlstra
2013-09-11 13:34 ` Mike Galbraith
2013-09-12 6:01 ` Mike Galbraith
2013-09-11 16:35 ` Andy Lutomirski
2013-09-11 18:05 ` Peter Zijlstra
2013-09-11 18:07 ` Andy Lutomirski
2013-09-11 11:14 ` Peter Zijlstra
2013-09-10 13:08 ` [PATCH 3/7] sched, arch: Create asm/preempt.h Peter Zijlstra
2013-09-10 13:08 ` [PATCH 4/7] sched: Create more preempt_count accessors Peter Zijlstra
2013-09-10 13:08 ` [PATCH 5/7] sched: Extract the basic add/sub preempt_count modifiers Peter Zijlstra
2013-09-10 13:08 ` [PATCH 6/7] sched, x86: Provide a per-cpu preempt_count implementation Peter Zijlstra
2013-09-10 13:27 ` Peter Zijlstra
2013-09-10 14:02 ` Eric Dumazet
2013-09-10 15:25 ` Peter Zijlstra
2013-09-10 16:48 ` Peter Zijlstra
2013-09-10 13:08 ` [PATCH 7/7] sched, x86: Optimize the preempt_schedule() call Peter Zijlstra
2013-09-10 13:42 ` Ingo Molnar
2013-09-10 13:55 ` Jan Beulich
2013-09-10 13:55 ` Jan Beulich
2013-09-10 14:25 ` Ingo Molnar
2013-09-10 13:51 ` [PATCH 0/7] preempt_count rework -v2 Ingo Molnar
2013-09-10 13:56 ` Ingo Molnar
2013-09-10 15:14 ` Peter Zijlstra
2013-09-10 15:29 ` Arjan van de Ven
2013-09-10 15:35 ` Peter Zijlstra
2013-09-10 16:24 ` Linus Torvalds
2013-09-11 16:00 ` H. Peter Anvin [this message]
2013-09-10 16:34 ` Linus Torvalds
2013-09-10 16:45 ` Peter Zijlstra
2013-09-10 17:06 ` Linus Torvalds
2013-09-10 21:25 ` Peter Zijlstra
2013-09-10 21:43 ` Linus Torvalds
2013-09-10 21:51 ` H. Peter Anvin
2013-09-10 22:02 ` Linus Torvalds
2013-09-10 22:06 ` H. Peter Anvin
2013-09-11 13:13 ` Peter Zijlstra
2013-09-11 13:26 ` Peter Zijlstra
2013-09-11 15:29 ` H. Peter Anvin
2013-09-11 15:33 ` Linus Torvalds
2013-09-11 18:59 ` Peter Zijlstra
2013-09-11 23:02 ` Linus Torvalds
2013-09-12 2:20 ` Peter Zijlstra
2013-09-12 2:43 ` Linus Torvalds
2013-09-12 11:51 ` Peter Zijlstra
2013-09-12 12:25 ` Ingo Molnar
2013-09-13 7:25 ` Kevin Easton
2013-09-13 8:06 ` Peter Zijlstra
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=5230939E.3050408@zytor.com \
--to=hpa@zytor.com \
--cc=ak@linux.intel.com \
--cc=arjan@linux.intel.com \
--cc=bitbucket@online.de \
--cc=fweisbec@gmail.com \
--cc=linux-arch@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mingo@kernel.org \
--cc=peterz@infradead.org \
--cc=tglx@linutronix.de \
--cc=torvalds@linux-foundation.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is an external index of several public inboxes,
see mirroring instructions on how to clone and mirror
all data and code used by this external index.