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From: Ingo Molnar <mingo@kernel.org>
To: Borislav Petkov <bp@alien8.de>
Cc: Andy Lutomirski <luto@amacapital.net>,
	Oleg Nesterov <oleg@redhat.com>, Rik van Riel <riel@redhat.com>,
	x86@kernel.org, linux-kernel@vger.kernel.org,
	Linus Torvalds <torvalds@linux-foundation.org>
Subject: Re: [RFC PATCH] x86, fpu: Use eagerfpu by default on all CPUs
Date: Sat, 21 Feb 2015 19:34:55 +0100	[thread overview]
Message-ID: <20150221183455.GC8406@gmail.com> (raw)
In-Reply-To: <20150221163840.GA32073@pd.tnic>


* Borislav Petkov <bp@alien8.de> wrote:

> plain 3.19:
>
>      234.681331200 seconds time elapsed                                          ( +-  0.15% )
>
> eagerfpu=ENABLE
>
>      234.066525648 seconds time elapsed                                          ( +-  0.19% )

hm, a win of more than 600 milliseconds - more than I'd 
have expected.

I really want to believe this, but I worry about the 
systematic boot-to-boot noise though, which cannot be 
eliminated via --repeat 10.

Would it be possible to add a simple runtime debug switch 
to switch between the two FPU modes dynamically via a 
sysctl?

It should not crash tasks I think if it's flipped around on 
a reasonably idle system, so should allow much better 
apples-to-apples comparisons with the same kind of page 
cache layout, etc.

Thanks,

	Ingo

  parent reply	other threads:[~2015-02-21 18:35 UTC|newest]

Thread overview: 45+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-02-20 18:58 [RFC PATCH] x86, fpu: Use eagerfpu by default on all CPUs Andy Lutomirski
2015-02-20 19:05 ` Borislav Petkov
2015-02-21  9:31 ` Ingo Molnar
2015-02-21 16:38   ` Borislav Petkov
2015-02-21 17:29     ` Borislav Petkov
2015-02-21 18:39       ` Ingo Molnar
2015-02-21 19:15         ` Borislav Petkov
2015-02-21 19:23           ` Ingo Molnar
2015-02-21 21:36             ` Borislav Petkov
2015-02-22  8:18               ` Ingo Molnar
2015-02-22  8:22                 ` Ingo Molnar
2015-02-22 10:48                 ` Borislav Petkov
2015-02-22 12:50                 ` Borislav Petkov
2015-02-22 12:57                   ` Ingo Molnar
2015-02-22 13:21                     ` Borislav Petkov
2015-02-22  0:34       ` Maciej W. Rozycki
2015-02-22  2:18         ` Andy Lutomirski
2015-02-22 11:06           ` Borislav Petkov
2015-02-23  1:45             ` Rik van Riel
2015-02-23  5:22               ` Andy Lutomirski
2015-02-23 12:51                 ` Rik van Riel
2015-02-23 15:03                   ` Borislav Petkov
2015-02-23 15:51                     ` Rik van Riel
2015-02-23 18:06                       ` Borislav Petkov
2015-02-23 21:17           ` Maciej W. Rozycki
2015-02-23 21:21             ` Rik van Riel
2015-02-23 22:14               ` Linus Torvalds
2015-02-24  0:56                 ` Maciej W. Rozycki
2015-02-24  0:59                   ` Andy Lutomirski
2015-02-23 22:27               ` Maciej W. Rozycki
2015-02-23 23:44                 ` Andy Lutomirski
2015-02-24  2:14                   ` Maciej W. Rozycki
2015-02-24  2:31                     ` Andy Lutomirski
2015-02-24 14:43                       ` Rik van Riel
2015-02-21 18:34     ` Ingo Molnar [this message]
2015-02-23 14:59 ` Oleg Nesterov
2015-02-23 15:11   ` Borislav Petkov
2015-02-23 15:53     ` Rik van Riel
2015-02-23 18:40       ` Oleg Nesterov
2015-02-24 19:15 ` Denys Vlasenko
2015-02-25  0:07   ` Andy Lutomirski
2015-02-25 10:37     ` Borislav Petkov
2015-02-25 10:50       ` Ingo Molnar
2015-02-25 10:45     ` Ingo Molnar
2015-02-25 17:12 ` Some results (was: Re: [RFC PATCH] x86, fpu: Use eagerfpu by default on all CPUs) Borislav Petkov

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