From: Linus Torvalds <torvalds@linux-foundation.org>
To: "H. Peter Anvin" <hpa@zytor.com>
Cc: Peter Zijlstra <peterz@infradead.org>,
Ingo Molnar <mingo@kernel.org>, Andi Kleen <ak@linux.intel.com>,
Mike Galbraith <bitbucket@online.de>,
Thomas Gleixner <tglx@linutronix.de>,
Arjan van de Ven <arjan@linux.intel.com>,
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: Tue, 10 Sep 2013 15:02:58 -0700 [thread overview]
Message-ID: <CA+55aFwabYsi=FvrAX+hqbpw5XUXqsokHn_Cyypv-JXmca6Q6Q@mail.gmail.com> (raw)
In-Reply-To: <522F9464.9070806@zytor.com>
On Tue, Sep 10, 2013 at 2:51 PM, H. Peter Anvin <hpa@zytor.com> wrote:
> On 09/10/2013 02:43 PM, Linus Torvalds wrote:
>
> Actually, the right thing here really is "er" (which I think you meant,
> but just to make it clear.)
Yes, I was just answering the i-vs-e confusion.
> "e" doesn't work on versions of gcc older than the first x86-64 release,
> but we don't care about that anymore.
Indeed.
> A final good question is if we should encapsulate the add/inc and
> sub/dec into a single function; one could easily do somethin glike:
Yes. However, I would do that at a higher level than the one that
builds the actual functions.
That said, there's a few cases where you might want to specify
add-vs-sub explicitly, but they are rather odd, namely the fact that
"-128" fits in a byte, but "128" does not.
So it can be better to add 128 by doing a "subl $-128" than by doing
an "add $128".
But we probably don't have any situation where we care about that
special value of "128". I've seen the trick, though.
Linus
next prev parent reply other threads:[~2013-09-10 22:02 UTC|newest]
Thread overview: 64+ 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 ` Peter Zijlstra
2013-09-10 13:08 ` [PATCH 1/7] sched: Introduce preempt_count accessor functions Peter Zijlstra
2013-09-10 13:08 ` 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 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 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
2013-09-11 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 ` Peter Zijlstra
2013-09-10 13:08 ` [PATCH 4/7] sched: Create more preempt_count accessors Peter Zijlstra
2013-09-10 13:08 ` 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 ` Peter Zijlstra
2013-09-10 13:08 ` [PATCH 6/7] sched, x86: Provide a per-cpu preempt_count implementation Peter Zijlstra
2013-09-10 13:08 ` 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 13:42 ` Ingo Molnar
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 13:51 ` 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
2013-09-10 16:34 ` Linus Torvalds
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 21:25 ` Peter Zijlstra
2013-09-10 21:43 ` Linus Torvalds
2013-09-10 21:51 ` H. Peter Anvin
2013-09-10 22:02 ` Linus Torvalds [this message]
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 13:26 ` Peter Zijlstra
2013-09-11 15:29 ` H. Peter Anvin
2013-09-11 15:33 ` Linus Torvalds
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
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