From: Jeremy Fitzhardinge <jeremy@goop.org>
To: Andi Kleen <ak@suse.de>
Cc: Arkadiusz Miskiewicz <arekm@maven.pl>, linux-kernel@vger.kernel.org
Subject: Re: proxy_pda was Re: What was in the x86 merge for .20
Date: Fri, 08 Dec 2006 13:34:37 -0800 [thread overview]
Message-ID: <4579DA6D.1030305@goop.org> (raw)
In-Reply-To: <200612082222.33673.ak@suse.de>
Andi Kleen wrote:
> The trouble is when it's CSEd it actually causes worse code because
> a register is tied up. That might not be worth the advantage of having it?
>
I think so, definitely; without proxy_pda you need to make it asm
volatile+mem clobber, which completely eliminates all optimisation
opportunities; in general the proxy_pda allows gcc to CSE and reorder
pda accesses. I guess in this case the memory writes inhibited the
overall CSE of current, so its just making do by CSEing the address.
> Hmm, maybe marking it volatile would help? Arkadiusz, does the following patch
> help?
>
Might work. But doesn't this make the pointed-at proxy_pda volatile,
not the proxy_pda pointer itself? Should it be something like (volatile
__T * volatile)?
J
next prev parent reply other threads:[~2006-12-08 21:34 UTC|newest]
Thread overview: 25+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-12-08 3:01 What was in the x86 merge for .20 Andi Kleen
2006-12-08 10:08 ` Andrew Morton
2006-12-08 10:44 ` Ingo Molnar
2006-12-08 16:41 ` Siddha, Suresh B
2006-12-08 17:10 ` Andi Kleen
2006-12-08 18:00 ` Siddha, Suresh B
2006-12-08 20:15 ` [discuss] " Andi Kleen
2006-12-09 8:41 ` Andrew Morton
2006-12-09 18:51 ` Andi Kleen
2006-12-08 17:12 ` Andi Kleen
2006-12-08 12:04 ` Arkadiusz Miskiewicz
2006-12-08 12:51 ` Muli Ben-Yehuda
2006-12-08 13:03 ` Arkadiusz Miskiewicz
2006-12-08 16:34 ` Muli Ben-Yehuda
2006-12-08 18:04 ` Andi Kleen
2006-12-08 18:10 ` Arkadiusz Miskiewicz
2006-12-08 20:07 ` Andi Kleen
2006-12-08 20:36 ` Jeremy Fitzhardinge
2006-12-08 20:35 ` Jeremy Fitzhardinge
2006-12-08 21:06 ` proxy_pda was " Andi Kleen
2006-12-08 21:09 ` Jeremy Fitzhardinge
2006-12-08 21:22 ` Andi Kleen
2006-12-08 21:34 ` Jeremy Fitzhardinge [this message]
2006-12-08 22:04 ` Arkadiusz Miskiewicz
-- strict thread matches above, loose matches on Subject: below --
2007-01-15 20:41 Paweł Sikora
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