From: Andi Kleen <ak@suse.de>
To: Linus Torvalds <torvalds@osdl.org>
Cc: Chuck Ebbert <76306.1226@compuserve.com>,
linux-kernel <linux-kernel@vger.kernel.org>,
Zachary Amsden <zach@vmware.com>
Subject: Re: [rfc patch] i386: don't save eflags on task switch
Date: Sat, 4 Nov 2006 02:36:20 +0100 [thread overview]
Message-ID: <200611040236.20478.ak@suse.de> (raw)
In-Reply-To: <Pine.LNX.4.64.0611031645141.25218@g5.osdl.org>
On Saturday 04 November 2006 01:46, Linus Torvalds wrote:
>
> On Fri, 3 Nov 2006, Chuck Ebbert wrote:
> >
> > There is no real need to save eflags in switch_to(). Instead,
> > we can keep a constant value in the and always
> > restore that.
>
> I don't really see the point. The "pushfl" isn't the expensive part, and
> it gives sane and expected semantics.
>
> The "popfl" is the expensive part, and that's the thing that can't really
> even be removed.
Well it could -- i made an attempt at it recently. But it would add
a little code to the SYSENTER entry code (basically a test / conditional
jump after the pushfl there) to clear any rogue flags on entry.
Not sure it is worth it. That is why i didn't put this patch in.
-Andi
next prev parent reply other threads:[~2006-11-04 1:36 UTC|newest]
Thread overview: 21+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-11-04 0:00 [rfc patch] i386: don't save eflags on task switch Chuck Ebbert
2006-11-04 0:46 ` Linus Torvalds
2006-11-04 1:36 ` Andi Kleen [this message]
-- strict thread matches above, loose matches on Subject: below --
2006-11-04 6:56 Chuck Ebbert
2006-11-04 19:09 ` Zachary Amsden
2006-11-04 19:35 ` Linus Torvalds
2006-11-05 3:55 ` Benjamin LaHaise
2006-11-05 4:13 ` Linus Torvalds
2006-11-05 5:41 ` Andi Kleen
2006-11-05 8:01 ` Zachary Amsden
2006-11-05 17:01 ` Andi Kleen
2006-11-05 17:26 ` Linus Torvalds
2006-11-05 17:34 ` Arjan van de Ven
2006-11-05 17:51 ` Linus Torvalds
2006-11-05 22:48 ` Zachary Amsden
2006-11-05 18:52 ` Andi Kleen
2006-11-05 16:12 ` Linus Torvalds
2006-11-05 16:54 ` Andi Kleen
2006-11-05 17:20 ` Linus Torvalds
2006-11-05 4:17 ` Zachary Amsden
2006-11-05 20:10 ` H. Peter Anvin
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