Re: [tip:x86/asm] x86: Prefer TZCNT over BFS

2012-09-17 Thread Jan Beulich
>>> On 17.09.12 at 19:05, "H. Peter Anvin" wrote: > Honestly, I don't see a reason to not do this unconditionally. On > anything but (pre-686-era) extremely old CPUs the cost of the extra > prefix is zero. On the really old CPUs the cost of the BSF instruction > will dwarf the penalty cycle for

Re: [tip:x86/asm] x86: Prefer TZCNT over BFS

2012-09-17 Thread Linus Torvalds
On Mon, Sep 17, 2012 at 10:05 AM, H. Peter Anvin wrote: > > Honestly, I don't see a reason to not do this unconditionally. Possibly. "unconditional" is certainly a lot saner than "conditionally on totally insane things". Linus -- To unsubscribe from this list: send the line "uns

Re: [tip:x86/asm] x86: Prefer TZCNT over BFS

2012-09-17 Thread H. Peter Anvin
On 09/17/2012 10:00 AM, Linus Torvalds wrote: \> > As Jan already pointed out, I really want more than that. > > The *conditions* for selecting X86_TZCNT have to be sane too. > > I really think that "32-bit generic kernel" is totally and completely > a wrong choice for enabling this. A 32-bit set

Re: [tip:x86/asm] x86: Prefer TZCNT over BFS

2012-09-17 Thread Linus Torvalds
On Mon, Sep 17, 2012 at 3:00 AM, Ingo Molnar wrote: > > Linus's suggestion is to introduce CONFIG_X86_TZCNT as an add-on > patch that cleans up and documents what this is all about. > > Would you be willing to do such a patch? As Jan already pointed out, I really want more than that. The *condit

Re: [tip:x86/asm] x86: Prefer TZCNT over BFS

2012-09-17 Thread Jan Beulich
>>> On 17.09.12 at 12:00, Ingo Molnar wrote: > Linus's suggestion is to introduce CONFIG_X86_TZCNT as an add-on > patch that cleans up and documents what this is all about. It wasn't just this he complained about. Plus I don't think the suggested name fits the current scheme - it would imply the

Re: [tip:x86/asm] x86: Prefer TZCNT over BFS

2012-09-17 Thread Ingo Molnar
* Jan Beulich wrote: > >>> On 14.09.12 at 23:14, Linus Torvalds > >>> wrote: > > On Thu, Sep 13, 2012 at 11:23 PM, tip-bot for Jan Beulich > > wrote: > >> > >> x86: Prefer TZCNT over BFS > > > > This patch is insane. > > I'm not going to defend this simple and strait forward a patch > to s

Re: [tip:x86/asm] x86: Prefer TZCNT over BFS

2012-09-17 Thread Jan Beulich
>>> On 14.09.12 at 23:14, Linus Torvalds wrote: > On Thu, Sep 13, 2012 at 11:23 PM, tip-bot for Jan Beulich > wrote: >> >> x86: Prefer TZCNT over BFS > > This patch is insane. I'm not going to defend this simple and strait forward a patch to such a reply, so Ingo, just drop it to please Linus,

Re: [tip:x86/asm] x86: Prefer TZCNT over BFS

2012-09-14 Thread Borislav Petkov
On Fri, Sep 14, 2012 at 02:14:57PM -0700, Linus Torvalds wrote: > On Thu, Sep 13, 2012 at 11:23 PM, tip-bot for Jan Beulich > wrote: > > > > x86: Prefer TZCNT over BFS > > This patch is insane. > > > For the moment, only do this when the respective generic-CPU > > option is selected (as there ar

Re: [tip:x86/asm] x86: Prefer TZCNT over BFS

2012-09-14 Thread Linus Torvalds
On Thu, Sep 13, 2012 at 11:23 PM, tip-bot for Jan Beulich wrote: > > x86: Prefer TZCNT over BFS This patch is insane. > For the moment, only do this when the respective generic-CPU > option is selected (as there are no specific-CPU options > covering the CPUs supporting TZCNT), and don't do that

[tip:x86/asm] x86: Prefer TZCNT over BFS

2012-09-13 Thread tip-bot for Jan Beulich
Commit-ID: 5870661c091e827973674cc3469b50c959008c2b Gitweb: http://git.kernel.org/tip/5870661c091e827973674cc3469b50c959008c2b Author: Jan Beulich AuthorDate: Mon, 10 Sep 2012 12:24:43 +0100 Committer: Ingo Molnar CommitDate: Thu, 13 Sep 2012 17:44:01 +0200 x86: Prefer TZCNT over BFS