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Re: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64()

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From: Linus Torvalds
Subject: Re: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64()
Date: Friday, March 26, 2010 - 10:42 am

On Fri, 26 Mar 2010, Scott Lurndal wrote:

Limiting it to x86-64 would certainly remove all the worries about all the 
historical x86 clones.

I'd still worry about it for future Intel chips, though. I absolutely 
_detest_ relying on undocumented features - it pretty much always ends up 
biting you eventually. And conditional writeback is actually pretty nasty 
from a microarchitectural standpoint.

			Linus
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Messages in current thread:
[PATCH 1/3] X86: Optimise fls(), ffs() and fls64(), David Howells, (Fri Mar 26, 7:42 am)
[PATCH 2/3] Adjust the comment on get_order() to describe ..., David Howells, (Fri Mar 26, 7:42 am)
[PATCH 3/3] Optimise get_order(), David Howells, (Fri Mar 26, 7:42 am)
Re: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64(), Linus Torvalds, (Fri Mar 26, 10:23 am)
Re: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64(), Scott Lurndal, (Fri Mar 26, 10:37 am)
Re: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64(), David Howells, (Fri Mar 26, 10:42 am)
Re: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64(), Linus Torvalds, (Fri Mar 26, 10:42 am)
Re: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64(), Linus Torvalds, (Fri Mar 26, 10:45 am)
Re: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64(), Matthew Wilcox, (Fri Mar 26, 10:52 am)
Re: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64(), Ralf Baechle, (Fri Mar 26, 10:58 am)
Re: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64(), Linus Torvalds, (Fri Mar 26, 11:03 am)
Re: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64(), Matthew Wilcox, (Fri Mar 26, 11:16 am)
Re: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64(), Matthew Wilcox, (Tue Apr 6, 6:30 am)
Re: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64(), Jamie Lokier, (Tue Apr 6, 6:57 am)
[No subject], Linus Torvalds, (Tue Apr 6, 7:40 am)
Re: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64(), David Howells, (Wed Apr 14, 4:49 am)
Re: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64(), David Howells, (Wed Apr 14, 6:13 am)
Re: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64(), Avi Kivity, (Wed Apr 14, 7:30 am)
Re: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64(), David Howells, (Thu Apr 15, 1:48 am)
Re: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64(), Avi Kivity, (Thu Apr 15, 1:49 am)
Re: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64(), Jamie Lokier, (Thu Apr 15, 4:41 am)